The suitable guidance law of air-to-air in Endgame must ensure that the missile with the minimum miss-distance hits the target implementing best escape strategy. Because the characteristic of maneuverable target is hard to be mastered, and in order to improve the hit accuracy of missile, it required the higher motor overload and the smaller time constant of missile flight control system in practical design of engineering. Thus introduce of reaction-jet control can obviously improve the missile maximum available overload, and reduce the time constant of missile flight control system. In this paper a variable structure guidance law is designed based on the proportional guidance law. Variable structure control system can provide the same features to overcome the influence of target maneuver, and achieve the goal of zero under the bounded maneuvering condition of LOS angular velocity, which made the ballistic flight to show the characteristics of parallel approaching method in the missile-after guidance process, and then it can improve the missile guidance performance. Analysis of the guidance loop on the stability and simulation analysis of the guidance system with or without the reaction-jet controller demonstrated that the miss-distance of the variable structure guidance law is smaller than PNG and the effect is better with reaction-jet controller.