Summary: Firstly, a three-order mathematical model of single-machine infinite power system is established and its dynamic behavior is discussed in brief. It is pointed out that the system may emerge chaos under certain conditions. Then, the passivity method is adopted to design a feedback stabilization controller and \(L_2\)-gain is adopted to restrain the disturbances, so as to stabilize the system in global approximately. The simulation results demonstrate the validity of this method. The studies show that the application of the method of excitation controller designed to improve the stability of power systems has a certain reference value. In the meantime, it has positive role in promoting the simulation application of Matlab in power system.