diff --git a/docs/design/2022-05-12-window-function.md b/docs/design/2022-05-12-window-function.md
index d04ab5edba9..400db878ca2 100644
--- a/docs/design/2022-05-12-window-function.md
+++ b/docs/design/2022-05-12-window-function.md
@@ -94,7 +94,7 @@ Children task's cost *= 0.05
 ### The Logic of Window Function in TiFlash
 #### Major additions
 - IWindowFunction
-  Defines execution functions of a window function(row_number, rank, dense_rank).
+  Defines execution functions of a window function(row_number, rank, dense_rank, lead, lag).
 - WindowDescription
   Define a window, including the name, frame, functions of a window.
 - WindowBlockInputStream
@@ -125,7 +125,7 @@ Children task's cost *= 0.05
 ##### Flow Chart
 ![tiflash-window-function-flow-chart](./images/tiflash-window-function-flow-chart.jpg)
 ### Support and Limit
-- Compared with TiDB, currently only  row_number, rank, dense_rank functions are supported.
+- Compared with TiDB, currently only row_number, rank, dense_rank, lead, lag functions are supported.
 
 |  Feature                                                                 |  support         |
 |  -----                                                                   |  -----           |
@@ -136,7 +136,7 @@ Children task's cost *= 0.05
 |  INTERVAL syntax for DateTime RANGE OFFSET frame                         |  Not supported   |
 |  Calculating aggregate functions over a frame                            |  Not supported   |
 |  rank(), dense_rank(), row_number()                                      |  Supported       |
-|  lag/lead(value, offset, default)                                        |  Not supported  |
+|  lag/lead(value, offset, default)                                        |  Supported       |
 
 - Compared with TiDB or MySQL, the result may have some differences.
   For example, compare the calculation results of TiFlash and TiDB: