This paper attempts to present an optimal design strategy and characteristics of high-power permanent magnet synchronous motor(PMSM) for direct-drive oil drilling mud pump. The structures of stator lamination, rotor lamination and stator winding are analyzed. And how temperature influences the performance of the motor is presented. Moreover, how to calculate air-gap length and the size of permanent magnet of high-power PMSM are discussed. The structure and design method of this motor can be used on other high-power PMSM.