Based on the contact dynamics of the hangers and rail, a finite element simulating method for missile rail launching from aircraft is presented, and the missile’s slip angle, shell stress and contact forces have been investigated. This method could consider the effects of aircraft’s movement, contact forces, aerodynamic forces and missile engine pressure, which can excellently simulate the real physical process of missile’s rail launching movement. The typical launching state of AIM-9 missile has been investigated, and the influences of aircraft’s vertical acceleration and roll rate, missile’s lateral aerodynamic force and yawing moment has been studied, the results can provide important basis for missile designing. This method is practical, accurate and easy to operate, it can be widely used in the security analysis of missile rail launching from aircraft.