The Application of nonlinear robust control law in microcomputer-based hydro-turbine governor is discussed and the mixed simulation test on the hydro-turbine governor is designed. The regulating effect of nonlinear robust control and conventional proportional integration differential（PID） control under different conditions is emphatically compared， such as short-circuit test， line clearing test， etc. Simulation results show that nonlinear robust control can play a good function in electric power system dynamic regulating during transient process， and has some superiority compared with conventional PID control.