Abstract: Aiming at the leakage of check valves in marine nuclear power plants, the effect of rapid temperature change on the check valves is studied by the fluid-solid-heat coupling simulation method. The results show that the equivalent stress and deformation of check valves are reduced with the decreasing of temperature, the maximum equivalent stresses of the sealing gasket and the quarter ring are at the ends of the valve pipe, and the maximum deformations are at the front and rear of the valve. The maximum deformation and shrinkage of the sealing gasket are larger than that of the quarter ring. Because of high temperature and pressure, there is a clear gap between the sealing gasket and the valve cover, and it can easily lead to leakage. The gap increases with the decreasing of temperature, which may intensify the leakage.