Abstract: The relationship among load capacity, rotating speed and material strength of axial magnetic bearing was studied. It suspends the rotor at the working position with magnetic force produced by control current. Therefore its working principle determines that its load capacity is proportional to the area of thrust disk. The locations of maximum shear stress and radial stress were found respectively by stress analysis of thrust disk. The result shows that the area of thrust disc is restricted by the maximum shear stress at the flange, and is proportional to strength of materials and inversely proportional to rotating speed. The maximum load capacity of axial magnetic bearing is determined by material strength and rotating speed, and it can be applied to the design of axial magnetic bearing in helium turbine system.