This paper presents a design technique to improve the power density and efficiency of a permanent magnet high-speed motor by using the mono-PM rotor. The suggested model minimized rotor diameter and stack length which have a bad influence on shafting in the high-speed operation. Conventional and suggested motors are analyzed and compared by using FEM(Finite Element Method) to verify the effectiveness. The overall performance such as torque, losses, efficiency and power density and so on are investigated in detail. The results of the analysis deduced that the suggested mono-PM rotor design is superior to the conventional one.