Voltage quality is one of important indicators of power quality, which has a major impact on the stability and safe operation of power grid. The control modes of automatic voltage control (AVC) are the decentralized control mode and centralized control mode.Voltage and reactive power control in master station includes the decentralized control mode and centralized control mode, too. Against the dynamic optimization control module of the system, this paper constructs the mathematical model,and uses improved improved economic voltage difference algorithm to seek the optimal control strategy of this model. The calculation of example indicates that the algorithm has a best accuracy and practicality.