Taking an offshore 6 MW medium-speed permanent magnet wind generator as the research object，the electromagnetic characteristics of the motor are simulated and analyzed for different electromagnetic schemes. The results show that the cogging torque generated by the unequal air gap skew-slot electromagnetic scheme is only 0.74% of the rated torque, and the line-voltage waveform distortion rate is 1.72%. The load characteristics and short circuit characteristics of the electromagnetic scheme can meet the requirements of product design. The air-to-air cooling scheme is adopted, and the feasibility of the scheme is verified by the analysis of temperature characteristics. According to the design scheme, two prototypes are made for test and verification. The test results of no-load voltage, no-load loss, temperature rise of stator winding and efficiency characteristics of the motor are basically consistent with the simulation analysis results, which verifies the rationality of the design.