The contact pressure of the endface seal of hydraulic rotary vane actuator（RVA）under different axial precompression was studied,and the stress and the influence of stress on the starting pressure of the RVA were analyzed.The mechanical analysis of the endface seal was performed using the elastic mechanics related formula,and the contact pressure generated by different axial precompression was calculated.Abaqus finite element simulation analysis software was used to simulate and analyze the end face seal made of polyurethane material,the strain and stress situation under different axial precompression was simulated,and the maximum strain and maximum stress location was found.The starting pressure of the RVA under different axial precompression was calculated,and the experiment was carried out to verify the accuracy of the theoretical analysis.The results show that the maximum strain and stress of the endface seal are distributed in the contact between the outer ring and the inner ring.When the axial precompression of the endface increases,the corresponding starting pressure of the RVA also increases,and the relationship between the two is nonlinear.