In order to improve the observation capabilities of astronomical telescopes, the aperture of the telescope's primary mirror is continuously increasing, while the requirements for its coating are becoming more stringent, necessitating a wider reflection bandwidth and higher reflectivity. Based on the domestic demand for astronomical telescopes, this article investigates a wide-spectrum high-reflection coating deposition technique for large-aperture mirrors using ion beam-assisted deposition technology. By analyzing the geometric configuration of the 3.2-meter coating equipment and the linear energy distribution area of the ion source, a dual-ion source partitioning and independent control method is adopted to achieve a coating layer with good consistency in optical constants within the range of a 2.5 m aperture spherical mirror. Starting from the actual shape of the 2.5 m primary mirror before coating, the height of the mirror surface when depositing the films is determined through simulation, and the shape and size of the correction plate are calculated to ensure that the uniformity of the coating layer is better than 1.2%. After designing the coating system, test pieces are placed at different positions in the simulated substrate for actual deposition. After testing, each test piece meets the design objectives. Based on the experimental results, the wide-spectrum high-reflectance coating of the 2.5 m primary mirror is finally completed using the 3.2-meter coating equipment and the ion beam-assisted deposition technology.