The high precision slotless disctype permanent magnet motor was studied. A threedimensional electromagnetic model of the machine was established. The back electromotive force and torque were analyzed. The eddy current losses of stator, rotor and permanent magnet caused by high order harmonics could be avoided. The thermal performance was improved and the foundation for further study could be provided. Then, the threedimensional temperature field model was built. The heat source distribution and heat transfer process were analyzed. The steady state temperature field distribution of the machine under natural heat dissipation condition was calculated. Finally, the validity and reasonability of the theoretical analysis were verified by the temperature rise experiment.