Abstract: With the expansion of the interconnected power system scale, low frequency oscillation problems of power system are more and more outstanding. Power system stabilizer (PSS) does well in suppressing low frequency oscillations, but also has its limitations. The robustness of PSS and many problems in multi-machine system cases are required to be solved. In this paper, a new controller designed by symmetric root locus (SRL) method is presented. By taking a single machine infinite bus system as an example, the SRL controller is designed. The root locus diagram and step response of SRL controller are drawn to validate its control effect by comparing with that of traditional PSS controller. Later, in order to further increase its feasibility in application, the dimension reduction is used to simplify control for SRL controller, which only keeps the component corresponding to rotation speed and angle. It can be concluded that the basic control effect of full order SRL controller is reached from the simulation results.