diff --git a/Tools/ModelTranslator/bl_decimate.py b/Tools/ModelTranslator/bl_decimate.py
index 5ec82626..c5dacf1b 100644
--- a/Tools/ModelTranslator/bl_decimate.py
+++ b/Tools/ModelTranslator/bl_decimate.py
@@ -289,18 +289,30 @@ def _uvpm_repack(obj, warnings):
 
 
 def _do_unwrap(obj, mode, warnings):
-    """按模式展开（排布默认 UVPM4 增强，失败保底内置 pack）；
-    seam 质量不达标自动回退 smart。返回 uv 指标 dict（含 mode）。"""
+    """按模式展开：seam 首选 66° 过门即用；否则扫 SEAM_ANGLE_SWEEP，
+    取过门且岛数最少者（重跑恢复其 UV）；全失败退 smart。排布 UVPM4 增强，
+    只在最终 UV 上跑一次，失败保底内置 pack。返回 uv 指标 dict（含 mode）。"""
     if mode == "seam":
-        _unwrap_seam(obj, warnings)
-        uvpm = _uvpm_repack(obj, warnings)
-        m = _collect_uv_metrics(obj)
-        if uv_gate_ok(m["flipped"], m["overlap"]):
-            m["mode"] = uvpm_mode_label("seam", uvpm)
+        angles = [SEAM_ANGLE_DEG] + list(SEAM_ANGLE_SWEEP)
+        candidates = []
+        for ang in angles:
+            _unwrap_seam(obj, warnings, seam_angle_deg=ang)
+            m = _collect_uv_metrics(obj)
+            m["angle"] = ang
+            candidates.append(m)
+            if uv_gate_ok(m["flipped"], m["overlap"]):
+                break   # 该档已过门；更低角度只会更碎，无需再试
+        best = pick_best_candidate(candidates)
+        if best is not None:
+            if best["angle"] != candidates[-1]["angle"]:
+                # 选中档不是最后跑的那档，重跑恢复其 UV（_unwrap_seam 会覆盖）
+                _unwrap_seam(obj, warnings, seam_angle_deg=best["angle"])
+            uvpm = _uvpm_repack(obj, warnings)
+            m = _collect_uv_metrics(obj)
+            m["mode"] = uvpm_mode_label("seam@%d" % int(best["angle"]), uvpm)
             return m
-        warnings.append("seam 展开质量不达标（翻转 %.1f%% 重叠 %s），回退 smart_project"
-                        % (m["flipped"] * 100,
-                           "%.1f%%" % (m["overlap"] * 100) if m["overlap"] is not None else "未知"))
+        warnings.append("所有 seam 角度（%s）均未过质量门，回退 smart_project"
+                        % "、".join("%d°" % int(a) for a in angles))
         mode = "smart_fallback"
     _unwrap_smart(obj)
     uvpm = _uvpm_repack(obj, warnings)