Abstract:This paper studies the film thickness of dynamic seals at the contact of vanes and cylinder which are used in swing motor. A mathematical model is established for the combined seal structure, and the film thickness in sealing gap is gotten by calculating the amount of each part’s deformation. The established mathematical model takes these factors, such as sealing pressure, relative sliding velocity as well as the physical characteristics of the seal on the film thickness, into account, which provides evidences for improving the dynamic sealing performance.