diff --git a/AstroLib/Include/AsAttitudeParam_2023.h b/AstroLib/Include/AsAttitudeParam_2023.h
index c714c38fa186509133fb5f51120ee7b55e46966b..ef35874c7e13b6a8dbf200fcf77a310f27a6fa10 100644
--- a/AstroLib/Include/AsAttitudeParam_2023.h
+++ b/AstroLib/Include/AsAttitudeParam_2023.h
@@ -158,6 +158,17 @@ void AsMtxToEuler132(const CMatrix<double>& mtx, CEuler& euler);
 ///***********************************************************************
 void AsMtxToEuler212(const CMatrix<double>& mtx, CEuler& euler);
 
+///***********************************************************************
+/// 方向余弦矩阵转为121转序Euler角
+/// @Author	Ma  Zihui
+/// @Date	2025.3
+/// @Input
+/// @Param	mtx		坐标转移矩阵
+/// @Output
+/// @Param	euler	欧拉角(rad)
+///***********************************************************************
+void AsMtxToEuler121(const CMatrix<double>& mtx, CEuler& euler);
+
 /***********************************************************************
 将四元数转化成欧拉角_132转序
  @Author	Xiong yanci