Abstract: The installation precision of the position and attitude measurement sensors directly affects the in-orbit measurement of the attitude of the sealed cabin and the control accuracy in the rendezvous and the docking process. In view of the difficulties of the in-orbit calibration and the complicated design constraints of the position and attitude sensors, various factors related with the systematic design are analyzed to guarantee the installation precision for the manned spacecraft, and these factors includes the influence of the parking tooling and the gravity, the cargo loading, the internal pressure, and the vibration during launching. A method is proposed for the high accuracy guarantee design by analyzing the integrative assessment of the multiple influencing factors. With the established objective function of the total installation precision as a comprehensive result of the precision variation under each single factor, the corresponding installation precision can be evaluated quantitatively with this method, to meet the requirement of the in-orbit measurement and control. The method has been successfully implemented on the Tianzhou series cargo spacecraft and is going to be used in the development of other manned spacecrafts.