In order to make the human-gun system has the best matching effect and to objectively evaluate the firing performance of the gun, the parameters that affect the firing precision of the human-gun system are discussed. According to single prone position has the characteristic of relying on over shoulder shooting, based on the theory of multiple rigid body system dynamics, the application of UG software, the simulated human body gun launch dynamics simulation model is established, analysis the effect of the movement characteristics of the automaton on the muzzle displacement during the firing of the human body gun frame, get the results of firing accuracy experiment, gas guide hole diameter and the complex spring stiffness which influence on firing precision are analyzed. Simulation results verify the feasibility and effectiveness of the model.