In order to study the feasibility of changing the semi-automatic firing mode into full-automatic firing mode on the basis of the structure of certain type of 18.4 multi-function riot gun, a dynamic simulation model was established by using three-dimensional mapping software and simulation software. The validity of the model was verified by comparing the simulation results of single shot with the experimental results, and on this basis, the simulation of continuous firing was carried out, and the simulation analysis of automatic cycle, ejection, ammunition feeding and other working conditions of the semi-automatic riot gun after the improvement of continuous firing function was carried out. The results show that the existing automatic circulation, ammunition feeding, ejection and other structures of the riot gun meet the requirements of continuous firing, and only the transmitter part of the riot gun needs to be slightly modified to achieve fully automatic firing.