diff --git a/backend/app/strategy/auto_usdc.py b/backend/app/strategy/auto_usdc.py
index 608ce44..2c18140 100644
--- a/backend/app/strategy/auto_usdc.py
+++ b/backend/app/strategy/auto_usdc.py
@@ -1,12 +1,14 @@
 """OKX 开仓前：交易账户 USDC 不足时市价 USDT→USDC（目标=期权所需×2）。
 
 仅 OKX SIM/LIVE。资金账户不参与；期权已可开则跳过。
+空仓等待开仓时也会按盘口刷新以损定仓名义后再检测，不依赖已选中合格期权。
 """
 
 from __future__ import annotations
 
 import logging
 import math
+import time
 from typing import Any
 
 from ..config import get_settings
@@ -19,6 +21,9 @@ logger = logging.getLogger(__name__)
 _TARGET_MULTIPLE = 2.0
 # 过小不兑（避免粉尘单）
 _MIN_CONVERT_USDT = 1.0
+# 不足时重试间隔，避免每秒砸单
+_RETRY_COOLDOWN_SEC = 45.0
+_last_attempt_ts: float = 0.0
 
 
 def _is_okx(exchange: str | None = None) -> bool:
@@ -40,10 +45,49 @@ def _round_down(n: float, nd: int = 2) -> float:
     return math.floor(n * f + 1e-12) / f
 
 
+def refresh_risk_sizing_from_market(db: Database | None = None) -> dict[str, Any]:
+    """空仓时用当前指数/卖一刷新以损定仓名义，便于资金门与自动兑对齐展示。"""
+    database = db or get_db()
+    out: dict[str, Any] = {"ok": True, "detail": "skip"}
+    try:
+        from ..sim.ledger import Ledger
+        from .open_capacity import _index_and_option_ask
+        from .risk_sizing import apply_risk_sizing_to_ledger, is_risk_based
+
+        if not is_risk_based(Ledger(database)):
+            out["detail"] = "manual_sizing"
+            return out
+        idx, ask = _index_and_option_ask()
+        if idx is None or ask is None or float(idx) <= 0 or float(ask) <= 0:
+            out["ok"] = False
+            out["detail"] = "暂无指数或期权卖一"
+            return out
+        r = apply_risk_sizing_to_ledger(
+            index_px=float(idx), option_ask=float(ask), db=database
+        )
+        out["ok"] = bool(r.ok)
+        out["detail"] = r.detail
+        out["k"] = r.k
+        out["option_qty_eth"] = r.option_qty_eth
+        return out
+    except Exception as e:
+        logger.exception("refresh risk sizing for auto_usdc failed")
+        return {"ok": False, "detail": str(e)}
+
+
+def prepare_okx_trading_usdc(db: Database | None = None) -> dict[str, Any]:
+    """选约前也可调用：先刷新名义，再按资金门自动兑 USDC。"""
+    database = db or get_db()
+    sized = refresh_risk_sizing_from_market(database)
+    top = ensure_okx_trading_usdc(database)
+    return {"sizing": sized, "convert": top}
+
+
 def ensure_okx_trading_usdc(
     db: Database | None = None,
     *,
     cap: dict[str, Any] | None = None,
+    force: bool = False,
 ) -> dict[str, Any]:
     """
     开仓资金门前调用：
@@ -51,6 +95,7 @@ def ensure_okx_trading_usdc(
     - 期权可开（USDC≥需）→ 跳过
     - 否则在**交易账户**市价 USDT→USDC，尽量补到 需×2（并预留永续保证金）
     """
+    global _last_attempt_ts
     db = db or get_db()
     out: dict[str, Any] = {
         "ok": True,
@@ -84,6 +129,19 @@ def ensure_okx_trading_usdc(
         out["capacity"] = cap
         return out
 
+    now = time.time()
+    if (
+        not force
+        and _last_attempt_ts > 0
+        and now - _last_attempt_ts < _RETRY_COOLDOWN_SEC
+    ):
+        left = _RETRY_COOLDOWN_SEC - (now - _last_attempt_ts)
+        out["detail"] = f"USDC 不足，自动兑换冷却中（{left:.0f}s）"
+        out["capacity"] = cap
+        out["need_usdc"] = round(need_f, 2)
+        out["have_usdc"] = round(have_f, 2)
+        return out
+
     target = need_f * _TARGET_MULTIPLE
     gap_usdc = target - have_f
     if gap_usdc <= 1e-6:
@@ -126,6 +184,7 @@ def ensure_okx_trading_usdc(
         out["capacity"] = cap
         return out
 
+    _last_attempt_ts = now
     s = get_settings()
     try:
         if s.is_sim:
@@ -163,9 +222,9 @@ def ensure_okx_trading_usdc(
         out["acted"] = False
         out["detail"] = f"自动兑换失败：{r.get('detail') or r}"
         out["raw"] = r
+        logger.warning("auto_usdc failed: %s", out["detail"])
         return out
 
-    # 兑换后重评
     invalidate_live_balance_cache()
     cap2 = assess_open_capacity(db)
     out.update(
diff --git a/backend/app/strategy/engine.py b/backend/app/strategy/engine.py
index be31e4b..4afced8 100644
--- a/backend/app/strategy/engine.py
+++ b/backend/app/strategy/engine.py
@@ -807,9 +807,44 @@ class StrategyEngine:
             self._set_state(phase="open", last_error="有未平仓，禁止开下一组")
             return
 
+        # OKX：先按盘口刷新名义并检测 USDC；不够则交易账户市价兑换（不依赖已选中合格期权）
+        try:
+            from .auto_usdc import prepare_okx_trading_usdc
+
+            prep = prepare_okx_trading_usdc(self.db)
+            conv = prep.get("convert") or {}
+            if conv.get("acted"):
+                self._set_state(
+                    last_error=None,
+                    phase="wait_signal",
+                )
+                logger.info("auto_usdc prepared: %s", conv.get("detail"))
+            elif conv.get("ok") is False and "不足" in str(conv.get("detail") or ""):
+                # 保留资金提示，但仍继续尝试选约（可能只是冷却/短暂失败）
+                logger.warning("auto_usdc: %s", conv.get("detail"))
+        except Exception:
+            logger.exception("prepare OKX USDC failed")
+
         self._set_state(phase="wait_signal")
         pick = await get_session().pick_for_open_async()
         if pick is None:
+            # 若期权仍不可开且刚才未兑成功，把资金状态写进错误，便于排查「为何没自动兑」
+            try:
+                from .open_capacity import assess_open_capacity
+
+                cap = assess_open_capacity(self.db)
+                if cap.get("option_can_open") is False:
+                    self._set_state(
+                        phase="wait_funds",
+                        last_error=(
+                            "无合格期权；且交易账户 USDC 不够开仓"
+                            f"（需≈{cap.get('option_need_usdc')}U / 有{cap.get('option_have_usdc')}U）。"
+                            "系统会在冷却后自动市价兑 USDC。"
+                        ),
+                    )
+                    return
+            except Exception:
+                pass
             self._set_state(
                 last_error="无合格期权：需剩余时长、杠杆（及已开启的ATM偏差）同时满足"
             )
@@ -842,11 +877,11 @@ class StrategyEngine:
             self._set_state(phase="idle", last_error="以损定仓计算异常，暂不开仓")
             return
 
-        # OKX：交易账户 USDC 不够开期权时，市价 USDT→USDC（目标=所需×2）；够则跳过
+        # 选约后名义可能变化，再检一次 USDC（force 跳过冷却，避免刚选完仍差一截）
         try:
             from .auto_usdc import ensure_okx_trading_usdc
 
-            ensure_okx_trading_usdc(self.db)
+            ensure_okx_trading_usdc(self.db, force=True)
         except Exception:
             logger.exception("auto USDC top-up failed")
 
diff --git a/docs/更新说明.md b/docs/更新说明.md
index 1c92215..39d538c 100644
--- a/docs/更新说明.md
+++ b/docs/更新说明.md
@@ -5,6 +5,15 @@
 
 ---
 
+## 2026-07-30 — 自动兑 USDC：不等待选约，USDC 不够即兑
+
+### 变更
+
+1. 策略空仓循环在选约**之前**先刷新以损定仓名义并检测交易账户 USDC；不够则市价兑换（不再因「无合格期权」跳过）。  
+2. 兑换失败/不足时错误提示会带上需/有 USDC；成功兑换有 45s 冷却防砸单。
+
+---
+
 ## 2026-07-30 — 手动兑换改走交易账户
 
 ### 变更