Based on the finite element software Ansys Workbench,the finite element model of the motion of the bump foil dynamic pressure gas bearing in the compressible fluid medium was established,and the fluid-structure coupling numerical simulation of the motion state of the bearing was carried out by using the 6DOF dynamic grid calculation method.The influence of different speed and bump foil structure parameters (length ratio,height and thickness of bump foil) on bearing performance was discussed.The simulation results show that the distribution of the bearing gas film pressure corresponds to the deformation of the flat foil,indicating that the proposed fluid-structure coupling method can effectively reflect the lubrication state of the bump foil dynamic pressure gas bearing.With the increase of rotational speed,the dynamic pressure effect of the bearing is enhanced continuously,the load-carrying capacity increases,and the structural deformation of flat foil is increased,resulting in fluctuations in the convergence zone of gas film pressure.With the increase of the length ratio of the bump foil and the thickness of the bump foil,the load-carrying capacity increases rapidly at first and then becomes stable,while the height of the bump foil has little effect on the load-carrying capacity,indicating that the load-carrying capacity can be improved by increasing the length ratio of the bump foil and the thickness of the bump foil appropriately.