Abstract: mization model for the difference coefficient of generator excitation system to improve grid operation voltage level during multi-period and reduce grid loss. The minimum voltage fluctuation at power grid pilot point during multi-period and the minimized active grid loss are taken as the objective functions, while the power flow equations are used as the constraints. The particle swarm optimization (PSO) algorithm is employed to solve the optimization model. The effects of the difference coefficients of generator excitation system on power grid operation voltage are analyzed in detail. The simulation results indicate that the operating voltage level of power grid can be effectively improved and the grid loss can be significantly reduced.