diff --git a/docs/en/12-taos-sql/10-function.md b/docs/en/12-taos-sql/10-function.md
index afcebcb818..b1c6f6c129 100644
--- a/docs/en/12-taos-sql/10-function.md
+++ b/docs/en/12-taos-sql/10-function.md
@@ -1209,27 +1209,40 @@ ignore_negative: {
 ### DIFF
 
 ```sql
-DIFF(expr [, ignore_negative])
+DIFF(expr [, ignore_option])
 
-ignore_negative: {
+ignore_option: {
     0
   | 1
+  | 2
+  | 3
 }
 ```
 
-**Description**: The different of each row with its previous row for a specific column. `ignore_negative` can be specified as 0 or 1, the default value is 1 if it's not specified. `1` means negative values are ignored. For tables with composite primary key, the data with the smallest primary key value is used to calculate the difference.
+**Description**: The different of each row with its previous row for a specific column. `ignore_option` takes the value of 0|1|2|3, the default value is 0 if it's not specified. 
+- `0` means that negative values ​​(diff results) are not ignored and null values ​​are not ignored
+- `1` means that negative values ​​(diff results) are treated as null values
+- `2` means that negative values ​​(diff results) are not ignored but null values ​​are ignored
+- `3` means that negative values ​​(diff results) are ignored and null values ​​are ignored
+- For tables with composite primary key, the data with the smallest primary key value is used to calculate the difference.
 
-**Return value type**:Same as the data type of the column being operated upon
+**Return value type**: `bool`, `timestamp` type and integer value type all return `int_64`, `floating` point type returns `double`, and if the diff result overflows, it is returned as overflow.
 
-**Applicable data types**: Numeric
+**Applicable data types**: Numeric type, timestamp and bool type.
 
 **Applicable table types**: standard tables and supertables
 
 **More explanation**:
 
-- The number of result rows is the number of rows subtracted by one, no output for the first row
-- It can be used together with a selected column. For example: select \_rowts, DIFF() from.
-
+- diff is to diff the data in current row and column with the **first valid data before**. The **first valid data before** refers to sorting by timestamp, searching current this row to the direction of smaller timestamps, checking the same column of other rows, and finding the first non-null data.
+- The diff result of numeric type is the corresponding difference; the timestamp is calculated based on the timestamp of the precision type of the database creation; the difference is calculated for bool type true as 1 and false as 0
+- When the row and column data does not exist (null), or no valid comparison data is found, the diff result is null
+- When ignoring negative values ​​(ignore_option is 1/3), if the diff result is negative, the result is set to null, and then filtered according to the null value filtering rule
+- When the diff result has a type overflow, the positive and negative results of the logical operation are used to determine whether to ignore the negative value. For example, the value of 9223372036854775800 - (-9223372036854775806) exceeds the range of BIGINT, and the diff result will display the overflow value -10, but it will not be ignored as a negative value
+- Supports single or multiple diffs in a single statement, and supports different diff functions to specify the same or different ignore_option , when there are multiple diffs, only when all diff results of a row are null and ignore_option is set to ignore null values, the row will be removed from the result set
+- Can be used with the selected associated columns. For example: select _rowts, DIFF() from.
+- When not using a composite primary key, the sub-tables of the super table may have the same timestamp data. If there are the same timestamps, it will prompt "Duplicate timestamps not allowed"
+- When using a composite primary key, the sub-tables of the super table may have the same composite primary key, whichever row is found first will prevail
 
 ### IRATE
 
diff --git a/docs/zh/12-taos-sql/10-function.md b/docs/zh/12-taos-sql/10-function.md
index 3e78ac0da0..ef63669458 100644
--- a/docs/zh/12-taos-sql/10-function.md
+++ b/docs/zh/12-taos-sql/10-function.md
@@ -1200,27 +1200,40 @@ ignore_negative: {
 ### DIFF
 
 ```sql
-DIFF(expr [, ignore_negative])
+DIFF(expr [, ignore_option])
 
-ignore_negative: {
+ignore_option: {
     0
   | 1
+  | 2
+  | 3
 }
 ```
 
-**功能说明**：统计表中某列的值与前一行对应值的差。 ignore_negative 取值为 0|1 , 可以不填，默认值为 0. 不忽略负值。ignore_negative 为 1 时表示忽略负数。对于你存在复合主键的表的查询，若时间戳相同的数据存在多条，则只有对应的复合主键最小的数据参与运算。
+**功能说明**：统计表中某列的值与之前行有效值的差。 ignore_option 取值为 0|1|2|3 , 可以不填，默认值为 0. 
+- 为 0 表示不忽略(diff结果)负值不忽略 null 值
+- 为 1 时则表示(diff结果)负值作为 null 值
+- 为 2 表示不忽略(diff结果)负值但忽略 null 值
+- 为 3 时则表示忽略(diff结果)负值且忽略 null 值
+- 对于存在复合主键的表的查询，若时间戳相同的数据存在多条，则只有对应的复合主键最小的数据参与运算。
 
-**返回数据类型**：同应用字段。
+**返回数据类型**：bool、时间戳类型及整型数值类型均返回 int_64，浮点类型返回 double, 若 diff 结果溢出则按溢出返回。
 
-**适用数据类型**：数值类型。
+**适用数据类型**：数值类型、时间戳和 bool 类型。
 
 **适用于**：表和超级表。
 
 **使用说明**:
 
-- 输出结果行数是范围内总行数减一，第一行没有结果输出。
-- 可以与选择相关联的列一起使用。 例如: select \_rowts, DIFF() from。
-
+- diff 是本行本列数据和之前最近的第一个有效数据做 diff，之前最近的第一个有效数据：指的是按照时间戳排序，从本行向较小的时间戳方向寻找，查看其他行的同一列，寻找到的第一个非 null 数据。
+- 数值类型 diff 结果为对应差值；时间戳根据创建数据库的精度类型的时间戳进行差值计算；bool 型 true 为1， false 为  0 进行差值计算
+- 当本行列数据不存在（为 null ）时，或者没找到有效的比较数据，diff 结果为 null
+- 忽略负值时（ ignore_option 为 1 / 3 ），如果 diff 结果为负值，则结果设置为 null，  然后根据 null 值过滤规则过滤
+- 当 diff 结果有类型溢出时，根据逻辑运算结果的正负进行判定是否忽略负值，例如 9223372036854775800  - (-9223372036854775806) 的值超出 BIGINT 的范围 ，diff 结果会显示溢出值 -10，但并不会被作为负值忽略
+- 支持单个语句中同时存在单个或者多个 diff，支持不同的 diff 函数指定相同或不同的 ignore_option ，当存在多个 diff 时只有当某行所有 diff 结果都为 null 且 ignore_option 都设置了忽略 null 值，该行才从结果集中剔除
+- 可以与选择相关联的列一起使用。 例如: select _rowts, DIFF() from。
+- 不使用复合主键时，超级表的子表可能会有相同时间戳数据，有相同的时间戳时，会提示 "Duplicate timestamps not allowed"
+- 使用复合主键时，超级表的子表可能有相同的复合主键，以首先找到的行数据为准
 
 ### IRATE