Abstract: This paper analyzes the influence of the ground gravity environment and the space pressure environment on the installation precision of the gyro assembly and the attitude-control and orbit-control sensors of manned spacecraft at different positions and in different states. The verification test shows that the analysis results are consistent with the experimental data. It is shown that the influence of the environmental differences on the equipment installation precision differs when the layout of equipment is different. Under the conditions of the no-load and the vertical parking conditions, the ground gravity environment has little effect on the installation precision of equipment. The installation precisions of the gyro assembly and the attitude-control and orbit-control sensor A are little affected by the space pressure environment, and the precision measurement results in the ground atmospheric environment can reflect the state of equipment on orbit, while the installation precisions of the attitude-control and orbit-control sensor B are obviously affected by the space pressure environment. The research may provide a reference for the layout and the precision measurement of spacecraft equipment.