In order to solve the practical problem of 24-hours dynamic reactive power optimization in power system dispatching, according to the limit output range of generator’s operation, this paper divides generator’s operation into three regions in PQ mathematical model and takes the action times of discrete control equipment as global inequality constraints, finally establishes a complete 24-hours non-linear mixed integer dynamic reactive power optimization mathematical model. The simulation results show that the mathematical model in this paper can adjust the output of the generators according to the actual situation effectively when the generators are in phase-leading operation. In addition, dynamic reactive power optimization reduces the number of control equipment’s action at the cost of increasing active power loss in the whole network. So, In order to ensure the safe and economic operation of power grid, it is necessary to coordinate the relationship between active power loss and the constraints of control equipment’s action. This paper has positive reference significance for power system dispatching.