diff --git a/server/app.mjs b/server/app.mjs
index 6687479..990bfa3 100644
--- a/server/app.mjs
+++ b/server/app.mjs
@@ -1233,6 +1233,25 @@ export function createAdminApp(services) {
     });
   });
 
+  adminApi.put('/users/:userId/image-quota', requireAdmin, async (req, res) => {
+    if (!subscriptionService?.setImageQuota) {
+      return res.status(503).json({ message: '图片额度服务未启用' });
+    }
+    const remaining = req.body?.remaining;
+    const total = req.body?.total;
+    const note = String(req.body?.note ?? '').trim();
+    const result = await subscriptionService.setImageQuota(
+      req.params.userId,
+      {
+        remaining: remaining === undefined || remaining === null ? null : Math.floor(Number(remaining)),
+        total: total === undefined || total === null ? null : Math.floor(Number(total)),
+      },
+      { operatorId: req.currentUser.id, note },
+    );
+    if (!result.ok) return res.status(400).json({ message: result.message });
+    res.json(result);
+  });
+
   adminApi.post('/users/:userId/image-quota/grant', requireAdmin, async (req, res) => {
     if (!subscriptionService?.grantImageQuota) {
       return res.status(503).json({ message: '图片额度服务未启用' });
diff --git a/src/admin/pages/UserDetailPage.tsx b/src/admin/pages/UserDetailPage.tsx
index 073b6a5..a7608c1 100644
--- a/src/admin/pages/UserDetailPage.tsx
+++ b/src/admin/pages/UserDetailPage.tsx
@@ -1,6 +1,6 @@
 import { useEffect, useState } from 'react';
 import { Link, Navigate, useParams } from 'react-router-dom';
-import { getAdminUser, rechargeUser, updateAdminUser, fetchUserImageQuota, grantUserImageQuota } from '../../api/client';
+import { getAdminUser, rechargeUser, updateAdminUser, fetchUserImageQuota, setUserImageQuota } from '../../api/client';
 import { CapabilitySettings } from '../../components/CapabilitySettings';
 import { PolicySettings } from '../../components/PolicySettings';
 import { SkillSettings } from '../../components/SkillSettings';
@@ -25,7 +25,7 @@ export function UserDetailPage() {
   const [spaceQuotaMb, setSpaceQuotaMb] = useState('5');
   const [imageQuota, setImageQuota] = useState<ImageQuotaView | null>(null);
   const [imageQuotaLoading, setImageQuotaLoading] = useState(false);
-  const [imageTotal, setImageTotal] = useState('');
+  const [imageRemaining, setImageRemaining] = useState('');
   const [imageGrantNote, setImageGrantNote] = useState('');
 
   useEffect(() => {
@@ -84,12 +84,12 @@ export function UserDetailPage() {
   }, [user?.id, user?.role]);
 
   useEffect(() => {
-    if (!imageQuota || imageQuota.unlimited || imageQuota.total == null) {
-      setImageTotal('');
+    if (!imageQuota || imageQuota.unlimited || imageQuota.remaining == null) {
+      setImageRemaining('');
       return;
     }
-    setImageTotal(String(imageQuota.total));
-  }, [imageQuota?.total, imageQuota?.unlimited]);
+    setImageRemaining(String(imageQuota.remaining));
+  }, [imageQuota?.remaining, imageQuota?.unlimited]);
 
   const handleRecharge = async (e: React.FormEvent) => {
     e.preventDefault();
@@ -123,25 +123,19 @@ export function UserDetailPage() {
       setLocalError('当前为无限额度套餐，无法在此调整');
       return;
     }
-    const targetTotal = Math.floor(Number(imageTotal));
-    if (!Number.isFinite(targetTotal) || targetTotal < 0) {
-      setLocalError('请输入非负整数总额度');
+    const targetRemaining = Math.floor(Number(imageRemaining));
+    if (!Number.isFinite(targetRemaining) || targetRemaining < 0) {
+      setLocalError('请输入非负整数剩余额度');
       return;
     }
-    if (targetTotal < imageQuota.used) {
-      setLocalError(`总额度不能低于已用量（${imageQuota.used} 张）`);
-      return;
-    }
-    const targetBonus = targetTotal - imageQuota.limit;
-    const delta = targetBonus - imageQuota.bonus;
-    if (delta === 0) {
+    if (targetRemaining === imageQuota.remaining) {
       setMessage('额度未变化');
       return;
     }
     try {
-      const result = await grantUserImageQuota(user.id, delta, imageGrantNote.trim());
+      const result = await setUserImageQuota(user.id, { remaining: targetRemaining }, imageGrantNote.trim());
       setImageQuota(result.quota);
-      setMessage('图片额度已更新');
+      setMessage(result.unchanged ? '额度未变化' : '图片额度已更新');
       setImageGrantNote('');
     } catch (err) {
       setLocalError(err instanceof Error ? err.message : '图片额度设置失败');
@@ -273,16 +267,16 @@ export function UserDetailPage() {
                   <p className="muted">{imageQuotaSummary || '暂无额度信息（用户可能尚无订阅）'}</p>
                 )}
                 <p className="muted">
-                  直接设置本周期图片总额度（套餐额度 + 额外充值）。已用量不变，修改后会反映在「充值」部分。
+                  直接设置本周期剩余可用张数。若目标低于当前套餐额度，会自动下调该用户的周期额度上限。
                 </p>
                 <form className="admin-form" onSubmit={handleImageQuotaSave}>
                   <input
-                    placeholder="图片总额度（张）"
+                    placeholder="剩余额度（张）"
                     type="number"
                     min="0"
                     step="1"
-                    value={imageTotal}
-                    onChange={(e) => setImageTotal(e.target.value)}
+                    value={imageRemaining}
+                    onChange={(e) => setImageRemaining(e.target.value)}
                     disabled={!imageQuota || imageQuota.unlimited}
                   />
                   <input
diff --git a/src/api/client.ts b/src/api/client.ts
index 4563396..c368ca6 100644
--- a/src/api/client.ts
+++ b/src/api/client.ts
@@ -1373,6 +1373,22 @@ export async function fetchUserImageQuota(userId: string) {
   }>(`/admin-api/users/${userId}/image-quota`);
 }
 
+export async function setUserImageQuota(
+  userId: string,
+  payload: { remaining?: number; total?: number },
+  note = '',
+) {
+  return portalFetch<{
+    ok: boolean;
+    unchanged?: boolean;
+    subscription: AdminSubscription;
+    quota: ImageQuotaView;
+  }>(`/admin-api/users/${userId}/image-quota`, {
+    method: 'PUT',
+    body: JSON.stringify({ ...payload, note }),
+  });
+}
+
 export async function grantUserImageQuota(userId: string, delta: number, note = '') {
   return portalFetch<{
     ok: boolean;