The working state of highpower and highspeed motor for energy storage flywheel were motor, generator and noload, to increase the efficiency of energy transformation of energy storage flywheel and to reduce the loss of motors in running were the main targets of electromagnetics design. Analyse winding loss, magnetic core loss and eddy current loss of highpower and highspeed motor for energy storage flywheel, concentrated on the influence of air gap to the stator eddy current loss. At the same time, a kind of cascade rotor permanent magnet structure could meet the low harmonics requirement of the permanent magnet synchronous motor (PMSM). The selection principle of rotor sheath material was proposed. Finally, an example was given to introduce the design analysis and calculation method of the motor.