采取主镜镜面向上真空蒸镀制备方式，开展了大型天文望远镜主镜铝加介质保护反射膜技术研究。结合ZZS3200型镀膜设备真空室几何配置，对传统膜厚分布计算物理模型进行了修正，分别分析了铝膜与介质膜层膜厚均匀性。结果表明:理论分析与实验数据一致，直径2.4 m范围内膜厚不均匀性约5.5%。通过优化工艺，成功制备出1.8 m平面镜薄膜元件，在350~1 800 nm波段范围内，膜层平均反射率88.6%，通过了环境稳定性测验。

The technology for coating the telescope primary mirror with protected aluminium layer is studied during the preparative process, when the mirror is face up. According to the geometry of ZZS3200 large coating equipment, the traditionally calculative model is modified, and the uniformity of the aluminium and dielectric layers is analyzed separately. The simulated results accord with the experimental results, and in the 2.4 m diameter range, the non-uniformity of the whole film is within 5.5%. The 1.8 m-diameter plane reflective primary mirror has been prepared with optimized technical parameters. Its reflectance after coating is 88.6% in the wavelength range from 350 to 1 800 nm. Furthermore, the films have passed the environment stability test successfully.