Abstract: Based on the actual structure of an IGBT module, the finite element equivalent thermal analysis model and the double thermal resistance model of the IGBT switch power supply are established. The total loss of the module is calculated by using the voltage-current curve and temperature measurement experiment results under the circumstance of actual work of the switching power supply. The transient thermal resistance which is the main parameter of the thermal characteristics is simulated. By comparing with the measured thermal resistance curve provided by the manufacturers data sheet, the consistence of both curves indicates that the finite element equivalent thermal analysis model is reasonable. The thermal distribution and chip junction temperature of the IGBT module are achieved under actual working state by experimental comparison and analysis, based on the steady state thermal simulation of the finite element analysis model and double thermal resistance model. The advantages and disadvantages of double thermal resistance model are analyzed, and an improvement program is proposed.