In response to environmental pollution and the energy crisis, large-scale tower solar thermal power as a sustainable alternative to traditional energy sources were explored. This article assumed a central absorption tower surrounded by a circular field of 6m×6m heliostats. The calculation of optical efficiency and thermal power output incorporated models for cosine efficiency, shadowing, and truncation efficiency. Key results include an annual average optical efficiency of 0.69, with a thermal power output of 74.61MW and 1.18KW/m² per unit mirror area. By capping the average output at 60MW and optimizing mirror dimensions and heliostat count, this article achieved a maximum annual average output of 1.20KW/m², utilizing 1050 heliostats with a 7m side length, leading to an average power output of 62.07MW.This article provides a research approach and framework for calculating the optical efficiency of a heliostat field, which also has theoretical guidance value for mirror field designers and contributes to the further development of tower-type solar thermal power generation technology.