diff --git a/README.md b/README.md
index 5c4ca3a..d673d8c 100644
--- a/README.md
+++ b/README.md
@@ -106,7 +106,7 @@ graph TB
 
 - 多参数、递归、struct 参数/返回值
 - 返回类型校验
-- `impl StructName { fn method(self: Type) -> Ret { ... } }`
+- `extend StructName { fn method(self: Type) -> Ret { ... } }`
 - `instance.method(args)` 调用
 - 内建函数：`print_i64`, `print_f64`, `print_bool`, `print_str`
 
diff --git a/docs/language-reference.md b/docs/language-reference.md
index 87784b9..704586b 100644
--- a/docs/language-reference.md
+++ b/docs/language-reference.md
@@ -297,10 +297,10 @@ fn print_point(p: Point) -> void {
 }
 ```
 
-### impl — 方法
+### extend — 方法
 
 ```rust
-impl Point {
+extend Point {
     fn new(x: i64, y: i64) -> Point {
         return Point { x: x, y: y };
     }
@@ -314,7 +314,7 @@ let p = Point.new(10, 20);   // 方法调用
 print_i64(p.get_x());        // 10
 ```
 
-- `impl StructName { fn ... }` 定义方法
+- `extend StructName { fn ... }` 为结构体扩展方法
 - 第一个参数必须是 `self: StructName`
 - 调用: `instance.method(args)`
 
@@ -456,7 +456,7 @@ struct Student {
     score: i64,
 }
 
-impl Student {
+extend Student {
     fn new(id: i64, score: i64) -> Student {
         return Student { name_id: id, score: score };
     }
@@ -570,7 +570,7 @@ l_lang.exe source.l --emit-ir
 函数:    fn name(p: T) -> Ret { return expr; }
 结构体:  struct Name { f: Type }   Name { f: val }
 枚举:    enum Name { A, B, C }     Name::B
-方法:    impl T { fn m(self: T) }  obj.m()
+方法:    extend T { fn m(self: T) }  obj.m()
 内建:    print_i64  print_f64  print_bool  print_str
 运算符:  + - * / %  == != < > <= >=  && || !  += -= *= /=
 注释:    // 行注释   /* 块注释 */
diff --git a/src/lexer/lexer.c b/src/lexer/lexer.c
index 9d55eaa..080e4d5 100644
--- a/src/lexer/lexer.c
+++ b/src/lexer/lexer.c
@@ -64,7 +64,7 @@ static TokenKind check_keyword(const Token* tok) {
     KW("bool",   TOK_BOOL);   KW("str",    TOK_STR);
     KW("void",   TOK_VOID);
     KW("struct", TOK_STRUCT); KW("type", TOK_TYPE);
-    KW("enum", TOK_ENUM);  KW("impl", TOK_IMPL);  KW("match", TOK_MATCH);
+    KW("enum", TOK_ENUM);  KW("extend", TOK_EXTEND);  KW("match", TOK_MATCH);
     KW("_", TOK_UNDERSCORE);
     KW("true",   TOK_TRUE);   KW("false",  TOK_FALSE);
     #undef KW
diff --git a/src/lexer/token.c b/src/lexer/token.c
index fcf7a73..2176c0d 100644
--- a/src/lexer/token.c
+++ b/src/lexer/token.c
@@ -7,7 +7,7 @@
 static const char* NAMES[] = {
     [TOK_FN] = "fn", [TOK_LET] = "let", [TOK_VAR] = "var", [TOK_IF] = "if",
     [TOK_ELSE] = "else", [TOK_WHILE] = "while", [TOK_FOR] = "for", [TOK_IN] = "in", [TOK_RETURN] = "return",
-    [TOK_STRUCT] = "struct", [TOK_TYPE] = "type", [TOK_ENUM] = "enum", [TOK_IMPL] = "impl",
+    [TOK_STRUCT] = "struct", [TOK_TYPE] = "type", [TOK_ENUM] = "enum", [TOK_EXTEND] = "extend",
     [TOK_MATCH] = "match",
     [TOK_I64] = "i64", [TOK_F64] = "f64", [TOK_BOOL] = "bool", [TOK_STR] = "str", [TOK_VOID] = "void",
     [TOK_INT_LIT] = "整数", [TOK_FLOAT_LIT] = "浮点数", [TOK_STR_LIT] = "字符串",
diff --git a/src/lexer/token.h b/src/lexer/token.h
index fb2e8d3..55cf139 100644
--- a/src/lexer/token.h
+++ b/src/lexer/token.h
@@ -7,7 +7,7 @@
 typedef enum {
     // 关键字
     TOK_FN, TOK_LET, TOK_VAR, TOK_IF, TOK_ELSE, TOK_WHILE, TOK_FOR, TOK_IN, TOK_RETURN,
-    TOK_STRUCT, TOK_TYPE, TOK_ENUM, TOK_IMPL, TOK_MATCH,
+    TOK_STRUCT, TOK_TYPE, TOK_ENUM, TOK_EXTEND, TOK_MATCH,
     // 类型关键字
     TOK_I64, TOK_F64, TOK_BOOL, TOK_STR, TOK_VOID,
     // 字面量
diff --git a/src/parser/parser.c b/src/parser/parser.c
index 00b84f3..9acec1f 100644
--- a/src/parser/parser.c
+++ b/src/parser/parser.c
@@ -777,21 +777,21 @@ AstNode* parse(Arena* a, const Token* tokens, size_t count,
             AstNode* enum_decl = ast_make_enum_decl(p.arena, arena_strdup_impl(p.arena, name->start, name->length), v_arr, vcount, tok_loc(name));
             if (enum_count >= 64) { error->message = "枚举过多 (最多64)"; error->filename = p.filename; error->line = peek(&p)->line; error->col = peek(&p)->col; return NULL; }
             enums[enum_count++] = enum_decl;
-        } else if (peek(&p)->kind == TOK_IMPL) {
+        } else if (peek(&p)->kind == TOK_EXTEND) {
             const Token* i_tok = advance(&p);
-            const Token* st_name = expect(&p, TOK_IDENT, error, "impl 后应为结构体名");
+            const Token* st_name = expect(&p, TOK_IDENT, error, "extend 后应为结构体名");
             if (!st_name) return NULL;
             if (!expect(&p, TOK_LBRACE, error, "缺少 '{'")) return NULL;
             AstNode* methods[64]; int mcount = 0;
             while (peek(&p)->kind != TOK_RBRACE && !error->message) {
                 if (mcount >= 64) { error->message = "方法过多 (最多64)"; error->filename = p.filename; error->line = peek(&p)->line; error->col = peek(&p)->col; return NULL; }
-                if (peek(&p)->kind != TOK_FN) { error->message = "impl 块内只允许 fn"; error->filename = p.filename; error->line = peek(&p)->line; error->col = peek(&p)->col; return NULL; }
+                if (peek(&p)->kind != TOK_FN) { error->message = "extend 块内只允许 fn"; error->filename = p.filename; error->line = peek(&p)->line; error->col = peek(&p)->col; return NULL; }
                 methods[mcount++] = parse_function(&p, error);
             }
             if (!expect(&p, TOK_RBRACE, error, "缺少 '}'")) return NULL;
             AstNode** m_arr = arena_alloc_impl(p.arena, mcount * sizeof(AstNode*));
             memcpy(m_arr, methods, mcount * sizeof(AstNode*));
-            if (impl_count >= 64) { error->message = "impl 块过多 (最多64)"; error->filename = p.filename; error->line = peek(&p)->line; error->col = peek(&p)->col; return NULL; }
+            if (impl_count >= 64) { error->message = "extend 块过多 (最多64)"; error->filename = p.filename; error->line = peek(&p)->line; error->col = peek(&p)->col; return NULL; }
             impls[impl_count++] = ast_make_impl_block(p.arena,
                 arena_strdup_impl(p.arena, st_name->start, st_name->length),
                 m_arr, mcount, tok_loc(i_tok));
@@ -799,7 +799,7 @@ AstNode* parse(Arena* a, const Token* tokens, size_t count,
             if (fn_count >= 256) { error->message = "函数过多 (最多256)"; error->filename = p.filename; error->line = peek(&p)->line; error->col = peek(&p)->col; return NULL; }
             functions[fn_count++] = parse_function(&p, error);
         } else {
-            error->message = "顶层只允许 fn、struct、type、enum 或 impl";
+            error->message = "顶层只允许 fn、struct、type、enum 或 extend";
             error->filename = p.filename;
             error->line = peek(&p)->line;
             error->col = peek(&p)->col;
diff --git a/test/programs/19_struct_method.l b/test/programs/19_struct_method.l
index c6f2c8b..f9a3793 100644
--- a/test/programs/19_struct_method.l
+++ b/test/programs/19_struct_method.l
@@ -1,6 +1,6 @@
 struct Point { x: i64, y: i64 }
 
-impl Point {
+extend Point {
     fn get_x(self: Point) -> i64 {
         return self.x;
     }
diff --git a/test/test_sema.c b/test/test_sema.c
index 16b19c7..ed7a986 100644
--- a/test/test_sema.c
+++ b/test/test_sema.c
@@ -335,7 +335,7 @@ void test_method_call_ok() {
     Arena a = arena_create(1);
     size_t tc; ErrorInfo lex_err = {0};
     Token* toks = lex(&a,
-        "struct Point { x: i64, y: i64 } impl Point { fn get_x(self: Point) -> i64 { return self.x; } } fn main() -> i64 { let p: Point = Point { x: 42, y: 0 }; return p.get_x(); }",
+        "struct Point { x: i64, y: i64 } extend Point { fn get_x(self: Point) -> i64 { return self.x; } } fn main() -> i64 { let p: Point = Point { x: 42, y: 0 }; return p.get_x(); }",
         "test", &tc, &lex_err);
     ASSERT(toks != NULL);
     ErrorInfo parse_err = {0};