Abstract: According to the problem that perpendicular impact on the target was required for reentry maneuvering warhead,the variable structure guidance law with terminal angular constraint was derived,which comprised diving-plane guidance equation and turning-plane guidance equation.Chattering Reduction was achieved on the basis of quasi-sliding mode control.Through computer simulation,the influence of the four guidance law parameters on the guidance performance was analyzed.Then the feasibility of off-line optimization on guidance law parameters by genetic algorithm was discussed and the effect of guidance law with optimal parameters was tested under the conditions of different initial state bias.Simulation results show that compared with optimal guidance law,the variable structure guidance law is more robust which can still hold the guidance precision even when disturbance exists.