This study aims to analyze the average efficiency and thermal power output of a heliostat field. A horizontal coordinate system and a mirror coordinate system are established with the center of the mirror field and the center of each heliostat as the origins, respectively. The study considers various factors including three types of shadowing and blockage scenarios, and spillage efficiency. Using rotation matrices and linear equations, a shadowing and blocking efficiency model is constructed. Combining the principles of concentration, ray tracing method, and geometric theory, the energy flux density is converted into a number of scatter points, and then a model for the various efficiencies and thermal power output of the heliostat field is established. Based on this, an optimization model is created with the objective of maximizing the average annual thermal power output per unit mirror area. A genetic algorithm based on a traversal strategy is used for solving this model, thereby facilitating the design of the parameters for the heliostats and the receiver tower in the heliostat field, improving the average annual thermal power output per unit mirror area, and providing assistance for theoretical research.