diff --git a/internal/service/package/reset_service.go b/internal/service/package/reset_service.go
index f1eadeb..ee87a8d 100644
--- a/internal/service/package/reset_service.go
+++ b/internal/service/package/reset_service.go
@@ -141,6 +141,10 @@ func (s *ResetService) resetMonthlyUsageWithDB(ctx context.Context, db *gorm.DB)
 
 	var resetPackages []*model.PackageUsage
 	err := db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
+		if err := s.backfillMissingMonthlyResetAt(tx, now); err != nil {
+			return err
+		}
+
 		var packages []*model.PackageUsage
 		err := tx.Where("data_reset_cycle = ?", constants.PackageDataResetMonthly).
 			Where("next_reset_at <= ?", now).
@@ -228,6 +232,66 @@ func (s *ResetService) resetMonthlyUsageWithDB(ctx context.Context, db *gorm.DB)
 	return nil
 }
 
+type monthlyResetBackfillCandidate struct {
+	ID             uint
+	ActivatedAt    *time.Time
+	ExpiresAt      *time.Time
+	CalendarType   string
+	DurationMonths int
+	DurationDays   int
+}
+
+// backfillMissingMonthlyResetAt 为迁移套餐补齐缺失的下次流量重置时间。
+func (s *ResetService) backfillMissingMonthlyResetAt(tx *gorm.DB, now time.Time) error {
+	var candidates []monthlyResetBackfillCandidate
+	if err := tx.Table("tb_package_usage AS usage").
+		Select("usage.id, usage.activated_at, usage.expires_at, pkg.calendar_type, pkg.duration_months, pkg.duration_days").
+		Joins("JOIN tb_package AS pkg ON pkg.id = usage.package_id AND pkg.deleted_at IS NULL").
+		Where("usage.data_reset_cycle = ?", constants.PackageDataResetMonthly).
+		Where("usage.next_reset_at IS NULL").
+		Where("usage.status IN ?", []int{constants.PackageUsageStatusActive, constants.PackageUsageStatusDepleted}).
+		Find(&candidates).Error; err != nil {
+		return errors.Wrap(errors.CodeDatabaseError, err, "查询待补齐重置时间的套餐失败")
+	}
+
+	for _, candidate := range candidates {
+		nextResetAt := calculateMissingMonthlyResetAt(candidate, now)
+		if nextResetAt == nil {
+			s.logger.Warn("缺少套餐计时信息，无法补齐月流量重置时间", zap.Uint("usage_id", candidate.ID))
+			continue
+		}
+
+		result := tx.Model(&model.PackageUsage{}).
+			Where("id = ? AND next_reset_at IS NULL", candidate.ID).
+			Update("next_reset_at", *nextResetAt)
+		if result.Error != nil {
+			return errors.Wrap(errors.CodeDatabaseError, result.Error, "补齐套餐月流量重置时间失败")
+		}
+		if result.RowsAffected > 0 {
+			s.logger.Info("已补齐套餐月流量重置时间",
+				zap.Uint("usage_id", candidate.ID),
+				zap.Time("next_reset_at", *nextResetAt))
+		}
+	}
+
+	return nil
+}
+
+func calculateMissingMonthlyResetAt(candidate monthlyResetBackfillCandidate, now time.Time) *time.Time {
+	activatedAt := now
+	if candidate.ActivatedAt != nil && !candidate.ActivatedAt.IsZero() {
+		activatedAt = *candidate.ActivatedAt
+	} else if candidate.CalendarType == constants.PackageCalendarTypeByDay {
+		validityDays := calculateByDayValidityDays(candidate.DurationMonths, candidate.DurationDays)
+		if candidate.ExpiresAt == nil || candidate.ExpiresAt.IsZero() || validityDays <= 0 {
+			return nil
+		}
+		activatedAt = candidate.ExpiresAt.AddDate(0, 0, -validityDays)
+	}
+
+	return CalculateNextResetTime(constants.PackageDataResetMonthly, candidate.CalendarType, now, activatedAt)
+}
+
 // ResetYearlyUsage 任务 11.6-11.7: 重置年流量
 func (s *ResetService) ResetYearlyUsage(ctx context.Context) error {
 	return s.resetYearlyUsageWithDB(ctx, s.db)