The design ideas and design characteristics of the vehiclemounted intermediate frequency high speed synchronous generator were elaborated. The test prototype was made according to the design idea and design characteristics. The binding and fixing of magnetic pole coil as well as the internal structure of threephase rotating rectifier were greatly improved in the process of prototype fabrication. Motor performances of the prototype were tested, and the effectiveness of the technical measures to improve the motor performances was verified. This research provided valuable experience for the future design of similar motor.