In order to study the sealing performance of the automobile brake pipe double flared pipe joint during the tightening process,an elastic-plastic material model was constructed with the help of finite element analysis method to study the influence of axial displacement load on the sealing performance.The friction torque of the pipe joint in the tightening process was analyzed,and the relationship formula between the axial tightening force and the torque was obtained.Combined with the metal multi-linear strengthening model and ANSYS nonlinear simulation,the dynamic change process of the stress and the contact surface pressure of the double flared pipe joint in the tightening process was analyzed.The validity of the simulation method was verified by torque high pressure leakage experiment.The results show that with the increase of displacement load,the maximum stress and deformation of the mushroom head of pipe joint increase,the pressure and sealing width of contact surface increase.The distribution area of contact pressure is stable,and two sealing rings are formed on the contact surface.With the increase of displacement load,the thickness of mushroom head decreases gradually,and its surface trench deepens.When the displacement load increases to a certain value,mushroom head may be cut off.