diff --git a/docs/source/sls/algorithm.rst b/docs/source/sls/algorithm.rst
index 81422b0a306811a666c30d11cdbd3370d64d4a6f..31f1a329306bf5abce86667ae92996a9e04ed75f 100644
--- a/docs/source/sls/algorithm.rst
+++ b/docs/source/sls/algorithm.rst
@@ -104,7 +104,7 @@ ERR数据单元构造误差数据，该步误差公式：
 
 .. math::
 
- \sigma = \sqrt{(SCI-bias)+{\sigma_bias}^2 + readnoise^2)} 
+ \sigma = \sqrt{(SCI-bias)+{\sigma_bias}^2 + readnoise^2} 
 
 
 **Dark correction**