Abstract: The IMU of Tianwen-1 is the core product of its navigation system; during the installation of gyro and accelerometer in IMU installation deviation and nonlinear scale factor occur, leading to the non-orthogonality of installation matrix and affecting the accuracy of IMU inertial navigation. In this paper, the orthogonality of gyro and accelerometer installation matrix was analyzed, and the orthogonalization algorithm of installation matrix for row vector was proposed, which improves the orthogonality of gyro and accelerometer installation matrix and reduces the distortion of installation error angle in the process of orthogonalization. The calibration test of IMU inertial navigation under typical working conditions was carried out. The test results show that after the installation matrix was orthogonalized according to row vector, the attitude accuracy of IMU inertial navigation was improved by 15.8%~54.7%, and the position accuracy was improved by 45.2%~85.7%. Adopting the above method, the percentage of static position and attitude performance improvement under various working conditions is consistent and not related to the test time; the percentage of dynamic position and attitude performance improvement under various working conditions is consistent and not related to the cumulative sum of rotation angle.