Abstract: When a low-orbit satellite moves under thermal condition, the normal line of the antenna mirror surface turns due to antenna mirror thermal distortion. The turn magnitude order is 100 μrad when the thermal tension is not released，so the beam transferred has a large deflect and the performance of the space-to-ground laser communication links will suffer seriously. Applying limited element analysis to analyze reasonable application of pressing-plate method shows that normal angle deviation of mirror body after the thermal tension being released can be 3 order magnitude smaller, and the beam direction deviation caused by thermal distortion can be well retarded.