Abstract: In view of the application of the virtual simulation technology in the assembly process design of manned spacecraft, this paper discusses the principle of the virtual simulation of the manned spacecraft assembly process and the basic procedures and methods of the manned spacecraft virtual assembly environment in the context of Tiangong-I target spacecraft's assembly process design. The concept, objective, methods, tools and application objects of the assembly process programming and the process scheme simulation analysis based on the virtual simulation technology are analyzed, together with the application methods of the virtual simulation in the assembly workshop and in the optimal design of the mechanical ground support equipment with practical examples. The actual application indicates that the virtual simulation technology can reduce the dependence of the assembly process design of manned spacecraft on the people’s experience, and achieve higher efficiency and better optimization.