Abstract: The stainless-steel plate heat sink, with its good low-temperature performance, the short production cycle and the low production cost, is widely used in the environmental simulation test facilities for spacecraft abroad. In order to have a good command of the hydro-bulging technique of the stainless-steel plate heat sink, the hydro-bulging of stainless-steel plate heat sink is numerically simulated by using a finite element model. The effects of the process parameters, including the rolling prestress, the boundary pressure and the solder joint layout, on the forming process, as well as the relationship between the forming pressure and the runner height and the height uniformity are investigated. The reasonable process parameters are obtained, to serve a guidance for the development and the production of the stainless-steel plate heat sink for the spacecraft thermal vacuum test. These results have been successfully applied to the development of more than one hundred sets of the heat sinks for space environmental simulators represented by the KM8.