diff --git a/lc498. Diagonal Traverse.py b/lc498. Diagonal Traverse.py
new file mode 100644
index 0000000..c30c3af
--- /dev/null
+++ b/lc498. Diagonal Traverse.py	
@@ -0,0 +1,46 @@
+class Solution:
+    def findDiagonalOrder(self, matrix):
+        """
+        :type matrix: List[List[int]]
+        :rtype: List[int]
+        """
+        if not matrix:
+            return matrix
+        direcs = [(-1, 1), (1, -1)]
+        d = 0
+        res = []
+        pos = [0, 0]
+        M = len(matrix)
+        N = len(matrix[0])
+        size = M * N
+        for i in range(size):
+            res.append(matrix[pos[0]][pos[1]])
+            pos[0] += direcs[d][0]
+            pos[1] += direcs[d][1]
+            # 顺序不能变，先判断是否超过右边和下边。也就是==M or ==N，
+            # 如果先判断是否==-1，那么在角上越界就会出错
+            if pos[0] == M:
+                pos[1] += 2
+                d = 1 - d
+                pos[0] = M - 1
+            elif pos[1] == N:
+                pos[1] = N - 1
+                d = 1 - d
+                pos[0] += 2
+            elif pos[0] == -1:
+                d = 1 - d
+                pos[0] = 0
+            elif pos[1] == -1:
+                d = 1 - d
+                pos[1] = 0
+
+        return res
+
+
+nums = [
+    [1, 2, 3],
+    [4, 5, 6],
+    [7, 8, 9]
+]
+s = Solution()
+print(s.findDiagonalOrder(nums))