Abstract: The paper introduces the research on the pressure control technology in the mirror chamber of solar imager, including theoretical analysis of mechanical dimensions of current-limiting orifice, design of valve for slow pressure relief, and pressure control simulation test of mirror chamber. At present, the developed slow pressure relief valve has been successfully delivered and put into use with the 46.5 nm extreme ultraviolet solar imager carried out on the Chinese Academy of Sciences’ Space New Technology Experiment Satellite.