A Oring performance testing device used in the static ring was developed.By using step motor to apply the axial load on the core axes through differential screw mechanism,this device can give pressure to the Oring in four directions,and then simulate the Oring seal between the static ring and the static ring seat.The contact stress and leakage of Nitrile rubber Oring under different working conditions were measured based on the device.The results show that,under certain precompression rate,the contact stress of Oring is increased with the increase of working medium pressure;In the case of certain working medium pressure,the contact stress of Oring is decreased with the increase of the precompression ratio,but the decreased amplitude is not so large.The inner diameter of the Oring has some effect on the contact stress under different conditions,but the influence is not big.