A joint optimization model of annual generation and maintenance considering security constraints and monthly electricity execution is proposed in this paper to solve the strong coupling between annual generation plan and annual maintenance plan in terms of system generation capacity and power flow constraints. The annual generation planning model takes days as the calculation period, and puts forward a method of electricity estimation combining historical load rate statistics with positive reserve constraints, which reduces the planning scale and improves the optimization efficiency. In order to consider the influence of maintenance plan on power grid operation, the power distribution factor of branch breaking is introduced. In the optimization model, the comprehensive influence of generation plan and maintenance plan on power flow can be considered simultaneously to enhance the joint optimization capability of generation plan and maintenance plan. The proposed model is applied to an actual power grid in a certain province in China, and the effectiveness of the proposed model is verified. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 5542dz170034) “Research and Application of Mid-long Term Maintenance Scheduling and Large-scale Power Delivery Coordinated Optimization Technique Considering Section Constraints”.