In this paper, first the new issues faced with in designing the guidance law and the shortcomings existing in the proportional navigation are analyzed, and then, to improve the performance of the PN, the information of the target maneuver acceleration of the interceptor is introduced to amending the classical proportional navigation law, and the parameters of the amended guidance law are optimized. Simulation results show that the new guidance law provides significant performance improvements over the commonly used classical proportional navigation law, and the overload distribution over the trajectory is reasonable.