To improve the rationality of operation mode of power grid with equipment maintenance plan, the optimization method with monthly maintenance plan of power transmission and transformation equipment is proposed. The problem is divided into two parts. One is generation and load sharing based on the balanced power capacity. The other is adjusting the active power flow by improving the rationality of the schedule. The problem of generation and load sharing includes the historical period load pattern, spare capacity of the generator, and transmission loss, etc. In the problem of adjusting the improvement of the rationality of the method, based on the iterative adjustment of the comprehensive sensitive index, the trend of convergence of the basic state, the static safety of the switching of N-1, stability constraint of the transient angle during N-1 fault are considered. By exploring the comprehensive problem and implementing it step by step, this paper gets the power grid operation mode which meets the engineering rationality under transmission and transformation maintenance plan and reduces the difficulty to solve the problem. The case based on the real power system verifies the proposed method.