By utilizing nonlinear finite element analysis software MSC.Marc,the material parameters of Odgen model were determined through curve fitting by using the experimental data of uniaxial tensile experiments of rubber like materials.The nonlinear finite element model of rubber O ring seals was set up and the influence of different medium pressure on the mechanical properties of rubber O ring seals was analyzed.The distribution of Von mises stress and contact stress on primary contact surface and side contact surface was achieved.The results show that with the increase of medium pressure,the Von mises stress is increased and transfered to the contact zone between rubber seal and groove,and its distribution on primary contact surface and side contact surface is approximate quadratic parabola.The maximum contact stress appears on the middle contact zone,and it is increased obviously with the increases of medium pressure.The maximum contact stress is greater than medium pressure,which can prevent the leakage of medium.