The application conditions of rail transit converter are relatively strict, which requires high reliability and service life of converter and IGBT devices.In order to improve the junction temperature of IGBT and the application life and reliability of the converter, a general loss calculation model Cord Strain Relief Protector was constructed based on the working mode of locomotive converter module to realize the on-line estimation of the junction temperature of IGBT devices of the converter; On this basis, combined with the application scenario of rail transit, a comprehensive active junction temperature control method was designed from the two dimensions Plush Collectibles of switching loss and heat dissipation system.Simulation and experiments showed that the implementation of active junction temperature control was feasible.