Based on the structure characteristics of bumptype bearing,new bumptype gas foil journal bearings of coupling top foil and bump foil was proposed,including three kinds of gas journal bearings that the foil covers the whole circle,the upper half circle and the lower half circle of the bearing separately.Considering the compressibility of air,the twodimensional gas flow of the bump foil bearing was simulated,the bearing capacity of the foil bearing was analyzed and compared with that of the rigid gas bearing.It is found that the bearing capacity of the bearing with foil covering the lower half circle is optimal.By changing the foil number,foil width and foil height of the bearing with foil covering the lower half circle,the change of the gas membrane flow field was further simulated.The simulation results show that under the condition of satisfying the stability of foil structure,the bearing capacity of the bearing with foil covering the lower half circle is increased with the increasing of the foil number and foil width,and it shows a sharp increase and then a slow decrease with the increasing of the foil height.