diff --git a/billing-subscription.mjs b/billing-subscription.mjs
index 584e343..6563256 100644
--- a/billing-subscription.mjs
+++ b/billing-subscription.mjs
@@ -704,6 +704,91 @@ export function createSubscriptionService(pool, { getPlanAsync = null } = {}) {
     }
   };
 
+  const setImageQuota = async (userId, { remaining = null, total = null } = {}, { operatorId = null, note = '' } = {}) => {
+    const hasRemaining = remaining !== null && remaining !== undefined;
+    const hasTotal = total !== null && total !== undefined;
+    if (hasRemaining === hasTotal) {
+      return { ok: false, message: '请指定 remaining 或 total 其中之一' };
+    }
+    const target = Math.floor(Number(hasRemaining ? remaining : total));
+    if (!Number.isFinite(target) || target < 0) {
+      return { ok: false, message: '额度必须是非负整数' };
+    }
+
+    const now = Date.now();
+    const conn = await pool.getConnection();
+    try {
+      await conn.beginTransaction();
+      const [rows] = await conn.query(
+        `SELECT * FROM h5_subscriptions
+         WHERE user_id = ? AND status = 'active' AND expires_at > ?
+         ORDER BY expires_at DESC LIMIT 1 FOR UPDATE`,
+        [userId, now],
+      );
+      const sub = mapSubRow(rows[0]);
+      if (!sub) {
+        await conn.rollback();
+        return { ok: false, message: '用户没有有效订阅，无法设置图片额度' };
+      }
+      if (sub.periodImagesLimit === 0) {
+        await conn.rollback();
+        return { ok: false, message: '无限额度套餐无法调整' };
+      }
+
+      const used = sub.periodImagesUsed;
+      const oldCapacity = sub.periodImagesLimit + sub.periodImagesBonus;
+      const oldRemaining = Math.max(0, oldCapacity - used);
+      const targetCapacity = hasRemaining ? used + target : target;
+      if (targetCapacity < used) {
+        await conn.rollback();
+        return { ok: false, message: `额度不能低于已用量（${used} 张）` };
+      }
+
+      let newLimit = sub.periodImagesLimit;
+      let newBonus = sub.periodImagesBonus;
+      if (targetCapacity >= sub.periodImagesLimit) {
+        newBonus = targetCapacity - sub.periodImagesLimit;
+      } else {
+        newLimit = targetCapacity;
+        newBonus = 0;
+      }
+
+      if (newLimit === sub.periodImagesLimit && newBonus === sub.periodImagesBonus) {
+        await conn.rollback();
+        return { ok: true, subscription: sub, quota: computeImageQuotaView(sub), unchanged: true };
+      }
+
+      await conn.query(
+        `UPDATE h5_subscriptions
+         SET period_images_limit = ?, period_images_bonus = ?, updated_at = ?
+         WHERE id = ?`,
+        [newLimit, newBonus, now, sub.id],
+      );
+      const updatedSub = {
+        ...sub,
+        periodImagesLimit: newLimit,
+        periodImagesBonus: newBonus,
+      };
+      const quota = computeImageQuotaView(updatedSub);
+      const ledgerDelta = hasRemaining ? target - oldRemaining : targetCapacity - oldCapacity;
+      await appendImageQuotaLedgerTx(conn, {
+        userId,
+        delta: ledgerDelta,
+        balanceAfter: quota.unlimited ? null : quota.remaining,
+        reason: 'admin_set',
+        operatorId,
+        note,
+      });
+      await conn.commit();
+      return { ok: true, subscription: updatedSub, quota };
+    } catch (err) {
+      await conn.rollback();
+      throw err;
+    } finally {
+      conn.release();
+    }
+  };
+
   const grantImageQuota = async (userId, delta, { operatorId = null, note = '' } = {}) => {
     const safeDelta = Math.floor(Number(delta));
     if (!Number.isFinite(safeDelta) || safeDelta === 0) {
@@ -820,6 +905,7 @@ export function createSubscriptionService(pool, { getPlanAsync = null } = {}) {
     consumeImageQuota,
     getImageQuota,
     checkImageQuota,
+    setImageQuota,
     grantImageQuota,
     listImageQuotaLedger,
     renewSubscription,
diff --git a/billing-subscription.test.mjs b/billing-subscription.test.mjs
index 59992ca..d9198d1 100644
--- a/billing-subscription.test.mjs
+++ b/billing-subscription.test.mjs
@@ -273,6 +273,52 @@ describe('createSubscriptionService', () => {
     });
   });
 
+  describe('setImageQuota', () => {
+    it('lowers remaining below plan limit by reducing period_images_limit', async () => {
+      const subRow = makeSubRow({
+        period_images_limit: 1000,
+        period_images_bonus: 0,
+        period_images_used: 32,
+      });
+      const pool = makePool(subRow);
+      const svc = createSubscriptionService(pool);
+      const result = await svc.setImageQuota('user-1', { remaining: 100 });
+      assert.equal(result.ok, true);
+      assert.equal(result.quota.remaining, 100);
+      assert.equal(result.quota.total, 132);
+      assert.ok(
+        pool._conn.queries.some(
+          ({ sql, params }) =>
+            sql.includes('SET period_images_limit = ?, period_images_bonus = ?') &&
+            params?.[0] === 132 &&
+            params?.[1] === 0,
+        ),
+      );
+    });
+
+    it('raises remaining above plan limit via bonus', async () => {
+      const subRow = makeSubRow({
+        period_images_limit: 50,
+        period_images_bonus: 0,
+        period_images_used: 10,
+      });
+      const pool = makePool(subRow);
+      const svc = createSubscriptionService(pool);
+      const result = await svc.setImageQuota('user-1', { remaining: 45 });
+      assert.equal(result.ok, true);
+      assert.equal(result.quota.remaining, 45);
+      assert.equal(result.quota.total, 55);
+      assert.ok(
+        pool._conn.queries.some(
+          ({ sql, params }) =>
+            sql.includes('SET period_images_limit = ?, period_images_bonus = ?') &&
+            params?.[0] === 50 &&
+            params?.[1] === 5,
+        ),
+      );
+    });
+  });
+
   describe('cancelSubscription', () => {
     it('returns cancelled=true when active sub exists', async () => {
       const pool = makePool(makeSubRow());