The DN350 wedge gate valve seat yield failure occurs when the inlet water temperature is 545 ℃ and the pressure is 10.3 MPa. In order to solve this problem, the finite element model was established, and the equivalent stress and total deformation nephogram of the valve seat were obtained by using the unidirectional fluidsolid coupling method. The results show that the pressure in the inner cavity flow field increases，the stress in the unloading groove of the outlet valve seat increases, resulting in yield failure, and the top of the outlet valve seat is concave inward;the distribution of stress on the valve seat can be optimized by increasing the number of unloading grooves,the seat stiffness can be increased and the deformation can be reduced by increasing the outer diameter of the valve seat;when the number of unloading grooves is 2, the outlet valve seat stress is reduced by 57.97% and the total deformation is reduced by 48.58%;seat stress can be reduced by increasing seat thickness, and the strength meets the requirements when the valve seat thickness is increased by 15 mm. The optimized valve seat meets the requirements of the actual working condition strength.This method provides reference for the improvement of similar structures.