To study the law of stress relaxation for O-ring and its sealing performance under stress relaxation,stress relaxation experiments were carried out on O-rings to obtain the attenuation rule of the axial loads.The value of these loads was taken into ANSYS to calculate the contact pressure of O-ring,and the leakage rate of O-ring sealing face was calculated by percolation theory.Results show that under stress relaxation,the axial load on the O-ring is decreased with time,larger initial force leads to sharper attenuation of axial load,and the axial load follows the attenuation rule of Fz=Aexp(-t/B)+C in general.Larger load applied on the O-ring results in bigger contact pressure between Oring and its contact surface,and the contact pressure is greater than the medium pressure.The leakage rate of O-ring sealing face is extremely small under stress relaxation.Experiment,simulation calculations,and theoretical analysis all show the good sealing performance of O-ring under stress relaxation,demonstrating the reliability of O-ring as static seal