The research on space laser communication has become a hotspot in recent years. The research trend of it is high speed transferring, networking and integration. Integration design means that the structure should be compact and reliable. CPA (Coarse Pointing Assembly) is an important component in space laser communication system. The paper makes design of CPA reflective mirror. On one hand, it is expected that the reflective mirror is as light as possible with small size. On the other hand, it is expected that the structure is reliable with high stiffness. These two aspects are contradict. And several factors make influence on these two aspects, such as the thickness of mirror, the size of bottom holes, the thickness of ribs and so on. The paper makes sensitivity analysis and chooses proper design variables for further optimization. And then, the paper makes a multi-objective optimal design based on factors mentioned above. In the process of optimization, a special objective function is deduced. At last the optimal design is obtained. The result shows that optimal design scheme has good characteristics. © 2019 SPIE.