To decrease the mass and power loss of axial hybrid magnetic bearings (HMBs) in the application of inertially stabilized platform (ISP) with a large axial diameter, this paper investigates the effects of the layout of axial HMBs and the degree of asymmetry (DOA). An asymmetry axial HMB is proposed for ISP based on DOA. Each single axial HMB is modeled and analyzed using the reluctance network method. And the relationship between current and force, as well as the displacement and force, are studied. Additionally, the optimization design method of the axial HMB is presented based on DOA. According to the principle of the design, the layout of the complete asymmetry axial HMB is designed with eight single axial HMBs in the upper end and four single axial HMBs in the lower end of ISP. Furthermore, the relationship among displacement, current and displacement stiffness and the relationship among displacement, current and current stiffness are analyzed as the DOA varies. A prototype is manufactured based on the above design and analysis, and experiments are carried out. Experimental results illustrate that the mass and power loss will be decreased dramatically compared to the symmetry layout of axial HMBs.Index Terms-Axial hybrid magnetic bearing, reluctance network method, inertially stabilized platform, degree of asymmetry.