The air-gap thickness is crucial to the operation of magnetic couplers,and it is of great significance for realizing speed adjustment of couplers through changing air-gap thickness. In order to investigate the relationship between air-gap thickness and adjustable-speed performance of axial-flux solid asynchronous magnetic couplers,a model for axial-flux magnetic couplers is established by combining equivalent magnetic circuit approach and Kirchhoff? s law of magnetic circuit. The magnetic circuit parameters of couplers are solved by utilizing the method of analytical calculation on the above model,then,the torque expression is obtained by integrating three-dimensional correction coefficient and torque formula. Moreover,by synthesizing the torque expression under constant torque load condition,the relationship between air-gap thickness and slip is derived,which is beneficial for acquiring the adjustable-speed relationship of axial-flux solid asynchronous magnetic couplers. The Matlab is used to solve the discretization of torque expression and adjustable-speed relationship,besides,the finite element simulations and experiments are also employed in the contrast and analyses,the accuracy of theoretical calculation is verified and the theoretical foundation for realizing precise speed adjustment of couplers is provided.