diff --git a/backend/internal/store/message_pg.go b/backend/internal/store/message_pg.go
new file mode 100644
index 0000000..8c1512a
--- /dev/null
+++ b/backend/internal/store/message_pg.go
@@ -0,0 +1,120 @@
+package store
+
+import (
+	"context"
+	"errors"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"github.com/hhs/camtalk/internal/models"
+)
+
+// PgMessageRepository 基于 PostgreSQL 的 MessageRepository 实现。
+type PgMessageRepository struct {
+	pool *pgxpool.Pool
+}
+
+// NewPgMessageRepository 创建 PgMessageRepository。
+func NewPgMessageRepository(pool *pgxpool.Pool) *PgMessageRepository {
+	return &PgMessageRepository{pool: pool}
+}
+
+func (r *PgMessageRepository) SaveMessage(ctx context.Context, sessionID string, msg models.Message, tokensUsed int) error {
+	_, err := r.pool.Exec(ctx,
+		`INSERT INTO messages (session_id, role, content, tokens_used) VALUES ($1, $2, $3, $4)`,
+		sessionID, msg.Role, msg.Content, tokensUsed,
+	)
+	return err
+}
+
+func (r *PgMessageRepository) GetMessages(ctx context.Context, sessionID string, limit int, beforeID int64) ([]StoredMessage, error) {
+	if limit <= 0 {
+		limit = 50
+	}
+
+	var rows []StoredMessage
+	var err error
+
+	if beforeID > 0 {
+		rows, err = r.queryMessages(ctx,
+			`SELECT id, session_id, role, content, tokens_used, created_at
+			 FROM messages
+			 WHERE session_id = $1 AND id < $2
+			 ORDER BY id DESC
+			 LIMIT $3`,
+			sessionID, beforeID, limit,
+		)
+	} else {
+		rows, err = r.queryMessages(ctx,
+			`SELECT id, session_id, role, content, tokens_used, created_at
+			 FROM messages
+			 WHERE session_id = $1
+			 ORDER BY id DESC
+			 LIMIT $2`,
+			sessionID, limit,
+		)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	// 反转为升序
+	for i, j := 0, len(rows)-1; i < j; i, j = i+1, j-1 {
+		rows[i], rows[j] = rows[j], rows[i]
+	}
+
+	return rows, nil
+}
+
+func (r *PgMessageRepository) queryMessages(ctx context.Context, query string, args ...any) ([]StoredMessage, error) {
+	pgxRows, err := r.pool.Query(ctx, query, args...)
+	if err != nil {
+		return nil, err
+	}
+	defer pgxRows.Close()
+
+	var messages []StoredMessage
+	for pgxRows.Next() {
+		var m StoredMessage
+		if err := pgxRows.Scan(&m.ID, &m.SessionID, &m.Role, &m.Content, &m.TokensUsed, &m.CreatedAt); err != nil {
+			return nil, err
+		}
+		messages = append(messages, m)
+	}
+	if err := pgxRows.Err(); err != nil {
+		return nil, err
+	}
+	return messages, nil
+}
+
+func (r *PgMessageRepository) GetLastMessage(ctx context.Context, sessionID string) (*StoredMessage, error) {
+	var m StoredMessage
+	err := r.pool.QueryRow(ctx,
+		`SELECT id, session_id, role, content, tokens_used, created_at
+		 FROM messages
+		 WHERE session_id = $1
+		 ORDER BY id DESC
+		 LIMIT 1`,
+		sessionID,
+	).Scan(&m.ID, &m.SessionID, &m.Role, &m.Content, &m.TokensUsed, &m.CreatedAt)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return nil, ErrMessageNotFound
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &m, nil
+}
+
+func (r *PgMessageRepository) GetMessageCount(ctx context.Context, sessionID string) (int, error) {
+	var count int
+	err := r.pool.QueryRow(ctx,
+		`SELECT COUNT(*) FROM messages WHERE session_id = $1`,
+		sessionID,
+	).Scan(&count)
+	if err != nil {
+		return 0, err
+	}
+	return count, nil
+}