According to the dynamic characteristics of a certain type of submachine gun during shooting, the rationality of the movement of related parts is analyzed. Based on the theory of multi-rigid-body dynamics, the virtual prototype model of the submachine gun is established by using UG, ADAMS and other software, and the dynamic simulation analysis of the submachine gun is carried out, including the process of firing, pushing the cartridge into the chamber, recoil, extraction and ejection. The displacement and velocity curves of the key parts in the whole process of motion are obtained. The numerical simulation results are compared with the experimental data, and the results show that the model is correct and feasible, which lays a foundation for further prototype verification and optimization.