In order to solve the problem of the recurrent damage of the thrust plate of the hybrid electric vehicle dynamic coupling system,the characteristics of lubricating oil film flow field between the friction surface of gear and the thrust plate in differential coupling system were studied.The variation trend of lubricating oil film of thrust mechanism was studied by changing the clearance between the gear and thrust plate.3D models of the gear and thrust plate were built by Creo software.Then Fluent was used to grid the gear,thrust plate and oil-gas mixed field inside the model,and the oil-gas mixed field was simulated and analyzed.The analysis shows that:the optimum clearance between gear and thrust plate friction surface is 0.1 mm,the flow field of lubricating oil film within the radius of thrust plate is better,and the fluctuation of the velocity field of oil-gas mixture is smaller.It is beneficial to prolong the service life of thrust plate.