Aimed at the sealing problem of large-diameter manholes and fuel tanks of spacecraft under extreme temperature,a three-dimensional analysis model of large-size energy storage sealing ring was established based on ANSYS.Through the study of compression resilience,linear load,and specific pressure distribution of the sealing contact surface at room temperature,it is obtained that the optimal compression ratio of the energy storage sealing ring should be about 20%,it is found that the optimal compression ratio should be about 20%.Under the optimal compression ratio of 20%,the sealing performance of the seal ring under low temperature (-196 ℃) and high temperature (176 ℃) working conditions was simulated and analyzed by finite element method.The results show that the sealing performance of the sealing ring under low temperature condition has no obvious change compared with that under the normal temperature,but it decreases to a certain extent under high temperature.The helium leak detection was carried out on the sealing ring under different pressure.it is found that the leakage under normal temperature conditions is less than that under low temperature and high temperature,and the change of seal leakage is small when the sealing pressure changes at the same temperature.The experimental result shows that the large diameter sealing ring has high requirements for the flatness of the sealing surface,and the installation and processing accuracy should be strictly controlled.