High-speed motors have the features of high current frequency, large stator core loss and large rotor eddy loss. The influential factors of core loss and rotor eddy loss are analyzed for the 10 kW, 100 000 r/min high-speed permanent magnet (PM) motor used in air compressor by comparing the effects of different magnetization methods (parallel and radial) and drive modes [driving by pulse amplitude modulation (PAM) square wave and SiC based pulse width modulation (PWM) sine wave]. Finite element analysis results indicate that the air gap flux harmonics of parallel magnetization are smaller, resulting in 40% smaller stator core loss compared with radial magnetization. Drive mode has a significant effect on motor losses especially on rotor loss. The rotor loss driving by sine wave is almost negligible, while it reaches 20% of the total losses when PM moter is driven by square wave because of the current harmonics. For the high rotor loss caused by square wave drive, further analysis is done by adding a copper shield on the rotor surface which can effectively reduce the eddy current loss. A high-speed motor with compressor load is tested under the control by two kinds of drivers to test the input active power on the DC bus. The results verify the influence of drive mode on motor losses.