Abstract: In order to solve the sealing failure of wedge-shaped double gate valve in the process of its practical application, the finite element model of gate valve was established by ANSYS software, and its thermal-mechanical coupling and sealing performance were analyzed in this paper. The results show that the maximum Mises stress appears at the outlet seat under the action of thermal stress and medium pressure. The evaluation results of three different stress strengths on the two dangerous paths of the outlet seat are not qualified, and the maximum sealing specific pressure at the sealing surface of the outlet seat exceeds the allowable specific pressure. Based on above mentioned analysis results, combined with the structure of the gate valve, the reasons for the sealing failure of the gate valve were figured out, and the gate valve was structurally optimized. It is indicated that after structural optimization, the maximum Mises stress at the outlet gate valve and the maximum sealing specific pressure at the sealing surface are greatly reduced and the evaluation results of three different stress strengths on the two dangerous paths are all qualified. Obviously, the problem of sealing failure is solved effectively after structural optimization. The research results can provide the reference for the structural design and optimization of wedge-shaped double gate valve.