diff --git a/docs/en/12-taos-sql/10-function.md b/docs/en/12-taos-sql/10-function.md
index f0daf4b82a2fdc9d519d151451a1bbd10fd93e31..f7ea906b5e4ba4daf8b40fae7bd01e613d7e14a0 100644
--- a/docs/en/12-taos-sql/10-function.md
+++ b/docs/en/12-taos-sql/10-function.md
@@ -877,6 +877,7 @@ INTERP(expr)
 - Interpolation is performed based on `FILL` parameter.
 - `INTERP` can only be used to interpolate in single timeline. So it must be used with `partition by tbname` when it's used on a STable.
 - Pseudo column `_irowts` can be used along with `INTERP` to return the timestamps associated with interpolation points(support after version 3.0.1.4).
+- Pseudo column `_isfilled` can be used along with `INTERP` to indicate whether the results are original records or data points generated by interpolation algorithm(support after version 3.0.2.1).
 
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diff --git a/docs/zh/12-taos-sql/10-function.md b/docs/zh/12-taos-sql/10-function.md
index afe90b8a93f5ef6f7b36d43619fb5ba222180ca3..cb99c83cc59aede3061ddc4a2c43278388961d8b 100644
--- a/docs/zh/12-taos-sql/10-function.md
+++ b/docs/zh/12-taos-sql/10-function.md
@@ -880,6 +880,7 @@ INTERP(expr)
 - INTERP 根据 FILL 字段来决定在每个符合输出条件的时刻如何进行插值。
 - INTERP 只能在一个时间序列内进行插值，因此当作用于超级表时必须跟 partition by tbname 一起使用。
 - INTERP 可以与伪列 _irowts 一起使用，返回插值点所对应的时间戳(3.0.1.4版本以后支持)。
+- INTERP 可以与伪列 _isfilled 一起使用，显示返回结果是否为原始记录或插值算法产生的数据(3.0.2.1版本以后支持)。
 
 ### LAST