As for the strong nonlinear and uncertain characteristic of the power system, based on the Extended-States-Observer and the variable structure control a nonlinear robust variable structure controller for Static Var Compensator(SVC), which can improve power angle stability of power system and local voltage characteristics of SVC, is proposed in the paper. The controller is robust to the change of network parameters and working point of system. The simulation suggests that the nonlinear robust variable structure controller can improve dynamic stability of power system effectively.