To research the influence of different gun’s automatic type on kinematic characteristics of shotgun automatic mechanisms, the kinematic characteristic analysis is based on a shotgun as an example. The principle of the automatic mechanisms is introduced; the virtual prototype model of the shotgun is established by three-dimensional modeling software and the ADAMS. The constraint relation, friction, contact and loads among components are properly set to research how the factor, such as inertial spring stiffness, internal ballistics and inertia constraint spring stiffness, influences the kinematic characteristics. The result shows that the chamber pressure, inertial spring stiffness and inertia constraint spring stiffness has a minimal effect; the automatic mechanism can operate reliably and steadily. But the spring-damping constraint on the gun body is different from the shooter’s shoulder, a further research is needed.