This paper presents a numerical model to evaluate the sealing performance of a combined seal, which consists an Oring and a PTFE bar. To better simulate the real working condition, many parameters like pressure, temperature, as well as material properties of the seal, are taken into consideration. This model is built based on the elastohydrodynamic lubrication (EHL) theory and can be used to calculate film thickness, the pressure distribution and the temperature field, thus can further provide theoretical basis for the problem of how to maintain an efficient lubrication with a lowest leakage rate.