Abstract: As an important part of the power system of a spacecraft, the solar cell array is studied in this paper based on the temperature conditions of the thermal vacuum reliability test. The thermal stress and the thermal deformation at the silver welding spot between the solar cell and the inter-link chip are analyzed. The results show that the thermal cycling can make the silver welding spots separate or contact, so the solar array can not work normally. The results provide some insight for the design and test for welding spot of a solar array.