IGBT modules are playing an increasingly important role, and their internal stress often affects the operating status and lifespan. This paper takes Infineon FF300R17KE3 IGBT module as the research object. Based on “Ansys”, an IGBT module simulation model under the coupling of electro, thermal and mechanical fields is established to simulate IGBT module under the operating state of power cycle conditions. By changing the simulation boundary conditions, this paper explores how the ambient temperature and humidity affect the internal stress of IGBT module, and compares changes in IGBT module junction temperature and internal stress under ambient temperature of 0°C, 25°C, and 50°C respectively. Then, change the humidity conditions while the ambient temperature is 25°C still. The IGBT module under dry air, normal humidity air and saturated air are simulated respectively, and the changes of stress are compared. The simulation results show that the stress of each part of the IGBT module will increase with the increase of ambient temperature. The ambient humidity has relatively small effect on the stress.