diff --git a/lib/common/static/options_panel.js b/lib/common/static/options_panel.js
index d9ff3c9..87e3017 100644
--- a/lib/common/static/options_panel.js
+++ b/lib/common/static/options_panel.js
@@ -280,8 +280,15 @@
     const mode = currentSizeMode();
     const sheetsEl = document.getElementById("opt-sheets-amount");
     const ethEl = document.getElementById("opt-eth-amount");
+    const hint = document.getElementById("opt-budget-full-hint");
+    const capEl = document.getElementById("opt-budget-full-cap");
     if (sheetsEl) sheetsEl.style.display = mode === "sheets" ? "" : "none";
     if (ethEl) ethEl.style.display = mode === "eth_amount" ? "" : "none";
+    if (hint) hint.style.display = mode === "budget_full" ? "" : "none";
+    if (capEl && root && root.dataset.tradeBudget) {
+      const n = Number(root.dataset.tradeBudget);
+      if (Number.isFinite(n) && n > 0) capEl.textContent = n.toFixed(2);
+    }
     document.querySelectorAll(".opt-size-mode-chip").forEach(function (chip) {
       const radio = chip.querySelector('input[name="opt-size-mode"]');
       chip.classList.toggle("is-selected", !!(radio && radio.checked));
diff --git a/lib/options/options_pricing_lib.py b/lib/options/options_pricing_lib.py
index b86117d..07daf8a 100644
--- a/lib/options/options_pricing_lib.py
+++ b/lib/options/options_pricing_lib.py
@@ -259,6 +259,11 @@ def eth_amount_from_sheets(sheets: int, ct_mult: float = 0.01) -> float:
     return round(int(sheets) * float(ct_mult), 8)
 
 
+def resolve_budget_full_usdc(trading_usdc: float, trade_budget_usdc: float) -> float:
+    """按可用余额打满:余额大于预算用预算,否则用余额."""
+    return min(float(trading_usdc), float(trade_budget_usdc))
+
+
 def calc_order_size(
     *,
     quote_per_unit: float,
diff --git a/lib/options/options_register.py b/lib/options/options_register.py
index 7888b77..c7ee833 100644
--- a/lib/options/options_register.py
+++ b/lib/options/options_register.py
@@ -163,13 +163,18 @@ def _require_options_ex(cfg: dict[str, Any]):
 
 
 def _budget_full_usdc(cfg: dict[str, Any], ex: Any) -> tuple[float | None, str]:
-    """交易账户 USDC 可用余额(由 calc_order_size 再乘 budget_buffer 留余量)."""
+    """打满可用额度 = min(交易户可用 USDC, 单笔预算);calc_order_size 再乘 budget_buffer."""
     from lib.exchange.okx_options_lib import fetch_options_trading_usdc
+    from lib.options.options_pricing_lib import resolve_budget_full_usdc
 
     raw = fetch_options_trading_usdc(ex)
     if raw is None or float(raw) <= 0:
         return None, "交易账户 USDC 可用余额不足"
-    return float(raw), ""
+    trading = float(raw)
+    cap = _env_float("OKX_OPTIONS_TRADE_BUDGET_USDC", float(cfg.get("trade_budget") or 10.0))
+    if cap <= 0:
+        return None, "单笔预算无效(OKX_OPTIONS_TRADE_BUDGET_USDC)"
+    return resolve_budget_full_usdc(trading, float(cap)), ""
 
 
 def _open_premium_paid(cfg: dict[str, Any], inst_id: str) -> float | None:
diff --git a/lib/options/templates/options_panel.html b/lib/options/templates/options_panel.html
index 2cf1ffb..d99f142 100644
--- a/lib/options/templates/options_panel.html
+++ b/lib/options/templates/options_panel.html
@@ -1,6 +1,7 @@
 <div class="options-page-wrap" style="grid-column:1/-1" id="options-root"
      data-default-underly="{{ options_default_underly | default('ETH') }}"
      data-budget-buffer="{{ options_budget_buffer | default(0.95) }}"
+     data-trade-budget="{{ options_trade_budget | default(10) }}"
      data-ask-liq-filter="{% if options_chain_ask_liq_filter is defined %}{{ '1' if options_chain_ask_liq_filter else '0' }}{% else %}1{% endif %}">
     {% if not options_enabled %}
     <div class="flash" style="margin-bottom:12px">期权 API 未启用:请在 <code>crypto_monitor_okx/.env</code> 设置 <code>OKX_OPTIONS_ENABLED=true</code> 及主账户 <code>OKX_OPTIONS_API_*</code>,然后 <code>pm2 restart crypto_okx --update-env</code>.</div>
@@ -18,7 +19,7 @@
                         <li>环境配置「链上仅显示有卖一」开启时,隐藏无真实卖一或深度不足 1 张的合约(估算价 <strong>~</strong> 亦不显示)。</li>
                         <li><strong>开仓只认真实卖一价且卖一深度≥1</strong>;无深度时面板显示参考标记价并禁用买入。</li>
                         <li>链展示近 <span id="opt-chain-dte">14</span> 日到期;<strong>T 型</strong>默认 ATM ±5 档,可展开全部。</li>
-                        <li>「按可用余额打满」可用额度 = min(交易 USDC × 预算缓冲 <strong id="opt-budget-buf">{{ '%.2f'|format(options_budget_buffer|default(0.95)|float) }}</strong>, 单笔预算);可在 env「预算缓冲比例」改。</li>
+                        <li>「按可用余额打满」可用额度 = min(交易户可用 USDC, 单笔预算 <strong id="opt-trade-budget">{{ '%.2f'|format(options_trade_budget|default(10)|float) }}</strong>),再 × 预算缓冲 <strong id="opt-budget-buf">{{ '%.2f'|format(options_budget_buffer|default(0.95)|float) }}</strong> 算张数(env 可改)。</li>
                         <li>平仓仅买一限价,详见说明文档。</li>
                     </ul>
                     <p><a href="/options/guide" target="_blank" rel="noopener">打开《期权开平仓与监控说明》</a></p>
@@ -133,6 +134,9 @@
                                     <input type="number" id="opt-eth-amount" min="0.01" step="0.01" placeholder="如 0.5" style="display:none"
                                            autocomplete="off" inputmode="decimal" data-lpignore="true" data-1p-ignore="true" data-form-type="other">
                                 </div>
+                                <p class="muted opt-budget-full-hint" id="opt-budget-full-hint" style="display:none;margin:6px 0 0;font-size:.82rem;line-height:1.4">
+                                    余额 &gt; 单笔预算(<span id="opt-budget-full-cap">{{ '%.2f'|format(options_trade_budget|default(10)|float) }}</span>U)时按预算;余额不足时按余额;再乘预算缓冲算张数。
+                                </p>
                                 <input type="text" id="opt-signal-note" name="opt_signal_note" class="opt-signal-note" placeholder="备注(关键位说明)"
                                        autocomplete="off" autocorrect="off" autocapitalize="off" spellcheck="false"
                                        data-lpignore="true" data-1p-ignore="true" data-form-type="other" readonly>
@@ -316,4 +320,4 @@
     </div>
 </div>
 <script src="/static/options_expiry_countdown.js?v=1"></script>
-<script src="/static/options_panel.js?v=49"></script>
+<script src="/static/options_panel.js?v=50"></script>
diff --git a/tests/test_options_budget_full.py b/tests/test_options_budget_full.py
new file mode 100644
index 0000000..579fd70
--- /dev/null
+++ b/tests/test_options_budget_full.py
@@ -0,0 +1,16 @@
+"""按可用余额打满:min(余额, 单笔预算)."""
+from __future__ import annotations
+
+from lib.options.options_pricing_lib import resolve_budget_full_usdc
+
+
+def test_balance_above_budget_uses_budget():
+    assert resolve_budget_full_usdc(100.0, 10.0) == 10.0
+
+
+def test_balance_below_budget_uses_balance():
+    assert resolve_budget_full_usdc(5.0, 10.0) == 5.0
+
+
+def test_balance_equals_budget():
+    assert resolve_budget_full_usdc(10.0, 10.0) == 10.0