The speed stability of external power motor affects fire ratio of chain gun heavily. The adaptive inversion controller is designed to satisfy the high performance of rotate speed of permanent magnet synchronous motor (PMSM) for chain gun system. Real-time adaptive parameter estimation is combined to restrain the effect of parametric uncertainty and load torque disturbance. Through design input control law to stator resistance, moment of inertia, friction coefficient, load torque, etc progress online estimation in the light of adaptive estimation law. The simulation results show the control strategy is perfect efficient to reduce the effect of variable parameter and load. This robust approach should be adopted in controlling of chain gun.