In order to reduce the cost and shorten the period of weapon research and development, an aerodynamic numerical model of gas-operated automatic weapon was established. The virtual prototype model of gas-operated automatic weapon was established by using UG and ADAMS software platform. The simulation analysis of the automatic mechanism was carried out, and the velocity and displacement curves of the automatic mechanism were obtained. The performance test of gas-operated automatic weapon was carried out, and the velocity and displacement curves of the automatic mechanism were measured by high-speed photography during live firing. By comparing the experimental data with the simulation data, the maximum error of the automatic machine speed is 1.5%, and the time error of the automatic machine reaching the maximum displacement is 8.2%. The experimental results are in good agreement with the simulation results, which is within the allowable error range. The results show that the test verifies the credibility of the simulation results, which can provide a reference for the research of gas-operated automatic weapons.