Abstract: Due to the advantages of the noncontact mechanism and adjustable support stiffness, the loss of magnetic bearings is low in small power class motor environment, and natural cooling can be adopted. For higher power class motors, the loss of magnetic bearings increases, necessitating the consideration of a cooling design. Taking the magnetic bearings of a megawatt-level HSPMG as the research object, considering the integrated state of radial and axial magnetic bearings and the actual internal environment of generator, the characteristics of temperature field of radial and axial magnetic bearings under natural cooling condition are studied based on fluid thermal coupling analysis. The result shows that the temperature of magnetic bearings is fairly high, and the stator and rotor of radial magnetic bearing have large thermal deformation, increasing the risk of safe operation. To solve the problem, considering the environment of motor and the structure of magnetic bearings, an integrated active cooling scheme is proposed, and the heat-flow field coupling simulation of the scheme is carried out. The result shows that the temperature of magnetic bearings decrease significantly, and the change of air gap of radial magnetic bearing is greatly reduced. Finally, the temperature rise test of the generator is carried out, and the test results are consistent with the simulation results.