Aiming at the special structure of the controllable excitation magnetic levitation linear synchronous motor used to drive the CNC machine tool, the magnetic-thermal coupling mechanism is studied. The influence of the magnetic field on the temperature rise of the motor at different armature currents is analyzed. The differential equation of heat conduction in the two-dimensional temperature field of the motor, the Newtonian cooling formula of heat convection and the boundary conditions of the temperature field are established. The thermal conductivity and convective heat transfer coefficient of different materials of the motor are determined, and the analytical expression of the convective heat transfer coefficient is given. Using ANSYS finite element simulation method in the magnetic-thermal coupling analysis, the main heat sources of the motor are analyzed. The ANSYS Maxwell software is used to calculate the motor stator and rotor losses, which are used as the motor heat source and imported into the Workbench software for thermal analysis to obtain the temperature distribution cloud diagram of the motor when different armature currents are applied. The simulation results show that the heat in the controllable excitation magnetic levitation linear synchronous motor is mainly concentrated in the windings，and the temperature increases with the increase of the armature current. The calculated data of temperature field can provide the basis for motor design.