分析了离轴三反射望远镜的杂散光特性，给出了遮光罩设计的基本原则并进行了初步的设计.根据系统所要探测到的极限星等，通过计算得到了望远镜光学系统的点源透射比所必需满足的条件；在Tracepro杂光分析软件中建模，在方位角为0°、45°、90°、135°和180°时分别对0.1°～80°之间共15个离轴角度进行了光线追迹,通过计算得到了系统的PST曲线.结果表明，系统PST整体上是下降的且在离轴角30°以后接近指标要求，但在方位角0°和180°时，PST曲线在个别角度有突增的现象，通过光线追迹数据，得到了主要的杂光传输路径，提出了对遮光罩的修改方案并对其进行了修改.最后对改进后的系统重新进行了仿真分析.仿真结果表明，系统的杂光抑制能力达到了指标要求.

The stray light properties of the off-axis three-mirror telescope was analyzed and the basic design principles of the light shade and baffle vanes were presented,then the design of them was discussed.According to the star that should be detected,the point source transmittance (PST) of the telescope was calculated and the maximum value beyond 30° were given.Then,the system model was built in the Tracepro stray light analysis software in which the light is traced according to the fifteen off-axis angles between 0.1° and 80°,at each azimuth angles of 0°、45°、90°、135° and 180°.Finally the PST curves were given,and the PST curves are going down in general and meet the requirements at most angles,but at the azimuth angles of 0°and 180°,the PST values increase at some angels.Then the main stray light paths were found by analyzing the ray-trace data of those angles and the methods to improve the light shade and baffle vanes were presented and made.Finally,the stray light repression ability of the off-axis three-mirror telescope meets the system requirements.