Abstract: In this paper, 300kW, 15 000r/min high speed permanent magnet synchronous motor is designed. For surface mounted respectively on high speed rotor structure, carbon fiber and alloy steel sheath of permanent magnet synchronous motor motor are analyzed. For high power and high speed permanent magnet motor, the parameters are designed and the temperature field and the loss are analyzed. Based on the finite element analysis, the software is used to simulate the motor, and the data such as iron loss are obtained, and the data obtained are analyzed. By comparing the simulation results, it is found that the heating of the motor under the alloy steel sheath is more serious.