This paper analyzes the chaotic phenomenon of a permanent magnet synchronous motor (PMSM) when it is turned off and what effect research parameters of PMSM have on chaos in the PMSM. Linear feedback controller is designed based on the inverse optimal control method. This method is simple and avoids a great amount of computation. In theory, a chaotic system can be asymptotically stable to zero by the controller. Numerical simulations further test the effectiveness of the theoretical analysis.