Abstract: The working principles of metro train regenerative braking energy (MRBE) feedback system is introduced, a structural scheme design of MRBE feedback converter based on modular design idea is presented. Through establishing a 3D simulation model of converter cabinet, the thermal filed of internal cooling system is analyzed, and the rationality of internal cooling system is verified through experiment of the converter temperature rise and wind velocity. The results show that the MRBE feedback converter could fulfill the product design requests and solve the problems of poor cooling effects in converter cabinet owing to the small size and light weight.