diff --git a/m3tpostprocess.py b/m3tpostprocess.py
index 3ff0952..c87ffb4 100644
--- a/m3tpostprocess.py
+++ b/m3tpostprocess.py
@@ -140,24 +140,31 @@ def process_circus_line(data: str) -> str:
 
 
 def replace_quote_str(s) -> str:
+    all_left_quotes = set(CJK_LEFT_QUOTE + NEED_REPLACED_LEFT_QUOTE)
+    all_right_quotes = set(CJK_RIGHT_QUOTE + NEED_REPLACED_RIGHT_QUOTE)
+    starts_with_left = len(s) > 0 and s[0] in all_left_quotes
+    ends_with_right = len(s) > 0 and s[-1] in all_right_quotes
+    # 引号只出现在头尾时（整个字符串被引号包裹），最外层使用「」；
+    # 否则最外层使用『』
+    offset = 0 if (starts_with_left and ends_with_right) else 1
     depth = 0
-    re = ""
+    result = ""
     for c in s:
         if c in CJK_LEFT_QUOTE:
-            re += CJK_LEFT_QUOTE[depth % 2]
+            result += CJK_LEFT_QUOTE[(depth + offset) % 2]
             depth += 1
         elif c in CJK_RIGHT_QUOTE:
             depth -= 1
-            re += CJK_RIGHT_QUOTE[depth % 2]
+            result += CJK_RIGHT_QUOTE[(depth + offset) % 2]
         elif c in NEED_REPLACED_LEFT_QUOTE:
-            re += CJK_LEFT_QUOTE[depth % 2]
+            result += CJK_LEFT_QUOTE[(depth + offset) % 2]
             depth += 1
         elif c in NEED_REPLACED_RIGHT_QUOTE:
             depth -= 1
-            re += CJK_RIGHT_QUOTE[depth % 2]
+            result += CJK_RIGHT_QUOTE[(depth + offset) % 2]
         else:
-            re += c
-    return re
+            result += c
+    return result
 
 
 def check_dialogue(source: str, target: str) -> str: