With the UML modelling language, this paper uses object-oriented “branch-refinement”, the screw type functional design. It designs a clear layered function system for the module funtions in mechanical model multi-angle of view hypothesized design assembly system, like virtual model design from multi-angles, interactive assembly interference examination and mechanical movement simulation demonstration. At the same time, it has used the MFC dynamic link module storehouse and the bidirectional iterative chain table in system's essence design, guaranting the nimble extendibility of the software system, which has laid a solid foundation for this system's procedure.