Power system stabilizer(PSS) is one of the most effective methods to restrain low frequency oscillation in power system.The paper studies into the synchronous generator excitation control with the power system stabilizer as the auxiliary control unit on the base of the analysis of existing synchronous generator excitation control system models.Thereafter a simulation model of an improved excitation control system including PSS is established based on Matlab.A test is carried out on the single machine infinite system for the cases of faults of three phase short circuit or disconnection,and the result show that the performance of the excitation control with PSS is superior to that of the excitation control without PSS.This design provides reference for the improvement of excitation system.