Power cycle test is a kind of life analysis experiment based on accelerated aging and also a kind of reliability study method. It plays a key role in the reliability study of large-capacity power electronics. In this paper a power cycle simulation study of a press-pack IGBT module based on semi-direct electrothermal coupling is presented, and electrothermal coupling steady state and transient state models are established, and the equivalent conductivity based on the power loss of the chip is derived. And the load setting is carried out by the method of equivalent conductivity, and the internal temperature distribution of the press-pack IGBT module during power cycling and the change with time are obtained. This method can effectively reduce the huge computational load caused by transient direct coupling and avoid the problem of iterative non-convergence, and it has a certaintheoretical guidance for power module reliability research and life prediction.