Abstract: A systematic study was conducted on the low-temperature sealing issue of the fourth-order O-ring in aviation actuators. Based on the rubber hardness characteristics, a two-parameter Mooney-Rivlin model was selected, and the parameters were determined through uniaxial tensile experiments. The assembly process was simulated using finite element analysis to investigate the effects of compression ratio and hardness on contact behavior. For the fourth-order structure, a thermo-elastic-plastic coupled finite element model was established to study the low-temperature response from −70 ℃ to room temperature, which was verified through low-temperature experiments. The results showed that under low pressure, to balance the sealing length and low contact stress, a scheme with a compression ratio greater than 20% and a hardness of 68-75 HS is recommended; under high pressure, a combination of a compression ratio of 15%-20% and a hardness of 75-83 HS is recommended. When the temperature rises from −40 ℃ to −20 ℃, the transition zone of the valve core step becomes a potential failure point due to stress concentration, and it bears the maximum equivalent stress and frictional load. The −70 ℃experimental verification showed that the contact pressure decreased by 0.873 MPa and the frictional stress decreased by 0.101 MPa, which highly matched the simulation, proving the effectiveness and engineering applicability of the model.