diff --git a/backend/go-service/app/contact/service/contact_service.go b/backend/go-service/app/contact/service/contact_service.go
new file mode 100644
index 0000000..63f8f57
--- /dev/null
+++ b/backend/go-service/app/contact/service/contact_service.go
@@ -0,0 +1,409 @@
+// Package service 提供 contact 模块的业务逻辑
+package service
+
+import (
+	"context"
+	"errors"
+
+	"github.com/echochat/backend/app/contact/dao"
+	"github.com/echochat/backend/app/dto"
+	"github.com/echochat/backend/pkg/logs"
+	"github.com/echochat/backend/pkg/ws"
+	"go.uber.org/zap"
+	"gorm.io/gorm"
+)
+
+var (
+	ErrSelfRequest      = errors.New("不能添加自己为好友")
+	ErrAlreadyFriend    = errors.New("已经是好友了")
+	ErrPendingExists    = errors.New("已有待处理的好友申请")
+	ErrBlocked          = errors.New("对方已将你拉黑")
+	ErrRequestNotFound  = errors.New("好友申请不存在")
+	ErrFriendNotFound   = errors.New("好友关系不存在")
+	ErrGroupNotFound    = errors.New("分组不存在")
+	ErrUserNotFound     = errors.New("用户不存在")
+)
+
+// ContactService 联系人业务服务
+type ContactService struct {
+	friendshipDAO  *dao.FriendshipDAO
+	friendGroupDAO *dao.FriendGroupDAO
+	pubsub         *ws.PubSub
+}
+
+// NewContactService 创建 ContactService 实例
+func NewContactService(
+	friendshipDAO *dao.FriendshipDAO,
+	friendGroupDAO *dao.FriendGroupDAO,
+	pubsub *ws.PubSub,
+) *ContactService {
+	return &ContactService{
+		friendshipDAO:  friendshipDAO,
+		friendGroupDAO: friendGroupDAO,
+		pubsub:         pubsub,
+	}
+}
+
+// SendFriendRequest 发送好友申请
+func (s *ContactService) SendFriendRequest(ctx context.Context, userID, targetID int64, message string) error {
+	funcName := "service.contact_service.SendFriendRequest"
+	logs.Info(ctx, funcName, "发送好友申请",
+		zap.Int64("user_id", userID), zap.Int64("target_id", targetID))
+
+	if userID == targetID {
+		return ErrSelfRequest
+	}
+
+	blocked, err := s.friendshipDAO.IsBlocked(ctx, userID, targetID)
+	if err != nil {
+		logs.Error(ctx, funcName, "检查拉黑状态失败", zap.Error(err))
+		return err
+	}
+	if blocked {
+		return ErrBlocked
+	}
+
+	isFriend, err := s.friendshipDAO.IsFriend(ctx, userID, targetID)
+	if err != nil {
+		return err
+	}
+	if isFriend {
+		return ErrAlreadyFriend
+	}
+
+	pending, err := s.friendshipDAO.HasPendingRequest(ctx, userID, targetID)
+	if err != nil {
+		return err
+	}
+	if pending {
+		return ErrPendingExists
+	}
+
+	_, err = s.friendshipDAO.CreateRequest(ctx, userID, targetID, message)
+	if err != nil {
+		return err
+	}
+
+	push := ws.NewPushMessage("notify.friend.request", map[string]interface{}{
+		"from_user_id": userID,
+		"message":      message,
+	})
+	if pubErr := s.pubsub.PublishToUser(ctx, targetID, push); pubErr != nil {
+		logs.Warn(ctx, funcName, "推送好友申请通知失败", zap.Error(pubErr))
+	}
+
+	return nil
+}
+
+// AcceptFriendRequest 接受好友申请
+func (s *ContactService) AcceptFriendRequest(ctx context.Context, requestID, userID int64) error {
+	funcName := "service.contact_service.AcceptFriendRequest"
+	logs.Info(ctx, funcName, "接受好友申请",
+		zap.Int64("request_id", requestID), zap.Int64("user_id", userID))
+
+	req, err := s.friendshipDAO.GetRequestByID(ctx, requestID)
+	if err != nil {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			return ErrRequestNotFound
+		}
+		return err
+	}
+
+	if req.FriendID != userID {
+		return ErrRequestNotFound
+	}
+
+	if err := s.friendshipDAO.AcceptRequest(ctx, requestID, userID); err != nil {
+		return err
+	}
+
+	push := ws.NewPushMessage("contact.request.accepted", map[string]interface{}{
+		"user_id": userID,
+	})
+	if pubErr := s.pubsub.PublishToUser(ctx, req.UserID, push); pubErr != nil {
+		logs.Warn(ctx, funcName, "推送申请接受通知失败", zap.Error(pubErr))
+	}
+
+	return nil
+}
+
+// RejectFriendRequest 拒绝好友申请
+func (s *ContactService) RejectFriendRequest(ctx context.Context, requestID, userID int64) error {
+	funcName := "service.contact_service.RejectFriendRequest"
+	logs.Info(ctx, funcName, "拒绝好友申请",
+		zap.Int64("request_id", requestID), zap.Int64("user_id", userID))
+
+	err := s.friendshipDAO.RejectRequest(ctx, requestID, userID)
+	if errors.Is(err, gorm.ErrRecordNotFound) {
+		return ErrRequestNotFound
+	}
+	return err
+}
+
+// GetFriendList 获取好友列表
+func (s *ContactService) GetFriendList(ctx context.Context, userID int64, groupID *int64) ([]dto.FriendInfo, error) {
+	funcName := "service.contact_service.GetFriendList"
+	logs.Debug(ctx, funcName, "获取好友列表", zap.Int64("user_id", userID))
+
+	friends, err := s.friendshipDAO.GetFriendList(ctx, userID, groupID)
+	if err != nil {
+		return nil, err
+	}
+
+	result := make([]dto.FriendInfo, 0, len(friends))
+	for _, f := range friends {
+		result = append(result, dto.FriendInfo{
+			ID:        f.ID,
+			UserID:    f.UserID,
+			Username:  f.Username,
+			Nickname:  f.Nickname,
+			Avatar:    f.Avatar,
+			Remark:    f.Remark,
+			GroupID:   f.GroupID,
+			CreatedAt: f.CreatedAt.Format("2006-01-02 15:04:05"),
+		})
+	}
+	return result, nil
+}
+
+// GetPendingRequests 获取待处理的好友申请
+func (s *ContactService) GetPendingRequests(ctx context.Context, userID int64) ([]dto.FriendRequestInfo, error) {
+	funcName := "service.contact_service.GetPendingRequests"
+	logs.Debug(ctx, funcName, "获取待处理申请", zap.Int64("user_id", userID))
+
+	requests, err := s.friendshipDAO.GetPendingRequests(ctx, userID)
+	if err != nil {
+		return nil, err
+	}
+
+	result := make([]dto.FriendRequestInfo, 0, len(requests))
+	for _, r := range requests {
+		result = append(result, dto.FriendRequestInfo{
+			ID:        r.ID,
+			UserID:    r.UserID,
+			Username:  r.Username,
+			Nickname:  r.Nickname,
+			Avatar:    r.Avatar,
+			Message:   r.Message,
+			Status:    r.Status,
+			CreatedAt: r.CreatedAt.Format("2006-01-02 15:04:05"),
+		})
+	}
+	return result, nil
+}
+
+// DeleteFriend 删除好友
+func (s *ContactService) DeleteFriend(ctx context.Context, userID, friendID int64) error {
+	funcName := "service.contact_service.DeleteFriend"
+	logs.Info(ctx, funcName, "删除好友",
+		zap.Int64("user_id", userID), zap.Int64("friend_id", friendID))
+	return s.friendshipDAO.DeleteFriend(ctx, userID, friendID)
+}
+
+// UpdateRemark 更新好友备注
+func (s *ContactService) UpdateRemark(ctx context.Context, userID, friendID int64, remark string) error {
+	funcName := "service.contact_service.UpdateRemark"
+	logs.Info(ctx, funcName, "更新好友备注",
+		zap.Int64("user_id", userID), zap.Int64("friend_id", friendID))
+	return s.friendshipDAO.UpdateRemark(ctx, userID, friendID, remark)
+}
+
+// BlockUser 拉黑用户
+func (s *ContactService) BlockUser(ctx context.Context, userID, targetID int64) error {
+	funcName := "service.contact_service.BlockUser"
+	logs.Info(ctx, funcName, "拉黑用户",
+		zap.Int64("user_id", userID), zap.Int64("target_id", targetID))
+
+	if userID == targetID {
+		return ErrSelfRequest
+	}
+	return s.friendshipDAO.BlockUser(ctx, userID, targetID)
+}
+
+// UnblockUser 取消拉黑
+func (s *ContactService) UnblockUser(ctx context.Context, userID, targetID int64) error {
+	funcName := "service.contact_service.UnblockUser"
+	logs.Info(ctx, funcName, "取消拉黑",
+		zap.Int64("user_id", userID), zap.Int64("target_id", targetID))
+	return s.friendshipDAO.UnblockUser(ctx, userID, targetID)
+}
+
+// GetBlockList 获取黑名单
+func (s *ContactService) GetBlockList(ctx context.Context, userID int64) ([]dto.FriendInfo, error) {
+	funcName := "service.contact_service.GetBlockList"
+	logs.Debug(ctx, funcName, "获取黑名单", zap.Int64("user_id", userID))
+
+	blocked, err := s.friendshipDAO.GetBlockList(ctx, userID)
+	if err != nil {
+		return nil, err
+	}
+
+	result := make([]dto.FriendInfo, 0, len(blocked))
+	for _, f := range blocked {
+		result = append(result, dto.FriendInfo{
+			ID:       f.ID,
+			UserID:   f.UserID,
+			Username: f.Username,
+			Nickname: f.Nickname,
+			Avatar:   f.Avatar,
+		})
+	}
+	return result, nil
+}
+
+// SearchUsers 搜索用户
+func (s *ContactService) SearchUsers(ctx context.Context, userID int64, keyword string, page, pageSize int) ([]dto.SearchUserInfo, int64, error) {
+	funcName := "service.contact_service.SearchUsers"
+	logs.Debug(ctx, funcName, "搜索用户", zap.String("keyword", keyword))
+
+	if page <= 0 {
+		page = 1
+	}
+	if pageSize <= 0 || pageSize > 50 {
+		pageSize = 20
+	}
+
+	users, total, err := s.friendshipDAO.SearchUsers(ctx, keyword, userID, page, pageSize)
+	if err != nil {
+		return nil, 0, err
+	}
+
+	friendIDs, _ := s.friendshipDAO.GetFriendIDs(ctx, userID)
+	friendSet := make(map[int64]bool, len(friendIDs))
+	for _, id := range friendIDs {
+		friendSet[id] = true
+	}
+
+	result := make([]dto.SearchUserInfo, 0, len(users))
+	for _, u := range users {
+		result = append(result, dto.SearchUserInfo{
+			ID:       u.ID,
+			Username: u.Username,
+			Nickname: u.Nickname,
+			Avatar:   u.Avatar,
+			IsFriend: friendSet[u.ID],
+		})
+	}
+	return result, total, nil
+}
+
+// GetRecommendFriends 好友推荐（基于共同好友）
+func (s *ContactService) GetRecommendFriends(ctx context.Context, userID int64) ([]dto.SearchUserInfo, error) {
+	funcName := "service.contact_service.GetRecommendFriends"
+	logs.Debug(ctx, funcName, "好友推荐", zap.Int64("user_id", userID))
+
+	friendIDs, err := s.friendshipDAO.GetFriendIDs(ctx, userID)
+	if err != nil {
+		return nil, err
+	}
+	if len(friendIDs) == 0 {
+		return []dto.SearchUserInfo{}, nil
+	}
+
+	candidateCount := make(map[int64]int)
+	friendSet := make(map[int64]bool, len(friendIDs))
+	for _, id := range friendIDs {
+		friendSet[id] = true
+	}
+
+	for _, fid := range friendIDs {
+		fofIDs, err := s.friendshipDAO.GetFriendIDs(ctx, fid)
+		if err != nil {
+			continue
+		}
+		for _, fof := range fofIDs {
+			if fof != userID && !friendSet[fof] {
+				candidateCount[fof]++
+			}
+		}
+	}
+
+	type candidate struct {
+		id    int64
+		count int
+	}
+	var candidates []candidate
+	for id, count := range candidateCount {
+		candidates = append(candidates, candidate{id: id, count: count})
+	}
+
+	limit := 10
+	if len(candidates) > limit {
+		for i := 0; i < limit; i++ {
+			for j := i + 1; j < len(candidates); j++ {
+				if candidates[j].count > candidates[i].count {
+					candidates[i], candidates[j] = candidates[j], candidates[i]
+				}
+			}
+		}
+		candidates = candidates[:limit]
+	}
+
+	result := make([]dto.SearchUserInfo, 0, len(candidates))
+	for _, c := range candidates {
+		users, _, err := s.friendshipDAO.SearchUsers(ctx, "", 0, 1, 1)
+		_ = users
+		_ = err
+		result = append(result, dto.SearchUserInfo{
+			ID: c.id,
+		})
+	}
+
+	return result, nil
+}
+
+// CreateGroup 创建好友分组
+func (s *ContactService) CreateGroup(ctx context.Context, userID int64, name string) (*dto.GroupInfo, error) {
+	funcName := "service.contact_service.CreateGroup"
+	logs.Info(ctx, funcName, "创建好友分组",
+		zap.Int64("user_id", userID), zap.String("name", name))
+
+	group, err := s.friendGroupDAO.CreateGroup(ctx, userID, name)
+	if err != nil {
+		return nil, err
+	}
+	return &dto.GroupInfo{
+		ID:        group.ID,
+		Name:      group.Name,
+		SortOrder: group.SortOrder,
+	}, nil
+}
+
+// GetGroups 获取好友分组列表
+func (s *ContactService) GetGroups(ctx context.Context, userID int64) ([]dto.GroupInfo, error) {
+	funcName := "service.contact_service.GetGroups"
+	logs.Debug(ctx, funcName, "获取好友分组", zap.Int64("user_id", userID))
+
+	groups, err := s.friendGroupDAO.GetGroups(ctx, userID)
+	if err != nil {
+		return nil, err
+	}
+
+	countMap, _ := s.friendshipDAO.CountFriendsByGroup(ctx, userID)
+
+	result := make([]dto.GroupInfo, 0, len(groups))
+	for _, g := range groups {
+		result = append(result, dto.GroupInfo{
+			ID:          g.ID,
+			Name:        g.Name,
+			SortOrder:   g.SortOrder,
+			FriendCount: countMap[g.ID],
+		})
+	}
+	return result, nil
+}
+
+// UpdateGroup 更新好友分组
+func (s *ContactService) UpdateGroup(ctx context.Context, userID, groupID int64, name string, sortOrder *int) error {
+	return s.friendGroupDAO.UpdateGroup(ctx, groupID, userID, name, sortOrder)
+}
+
+// DeleteGroup 删除好友分组
+func (s *ContactService) DeleteGroup(ctx context.Context, userID, groupID int64) error {
+	return s.friendGroupDAO.DeleteGroup(ctx, groupID, userID)
+}
+
+// MoveToGroup 移动好友到分组
+func (s *ContactService) MoveToGroup(ctx context.Context, userID, friendID int64, groupID *int64) error {
+	return s.friendGroupDAO.MoveToGroup(ctx, userID, friendID, groupID)
+}