diff --git a/problems/0509.斐波那契数.md b/problems/0509.斐波那契数.md
index 8be11312..112c96f9 100644
--- a/problems/0509.斐波那契数.md
+++ b/problems/0509.斐波那契数.md
@@ -187,7 +187,24 @@ class Solution {
 ```
 
 Python：
+```python3
+class Solution:
+    def fib(self, n: int) -> int:
+        if n < 2:
+            return n
+        a, b, c = 0, 1, 0
+        for i in range(1, n):
+            c = a + b
+            a, b = b, c
+        return c
 
+# 递归实现
+class Solution:
+    def fib(self, n: int) -> int:
+        if n < 2:
+            return n
+        return self.fib(n - 1) + self.fib(n - 2)
+```
 
 Go：