Abstract: The stable operation of power devices is an important guarantee for the reliable operation of the rectifier, and the life prediction of power devices is also an effective means to improve the reliability of the system. However, in the current life assessment,only the continuous working life of the device is predicted, and the change of thermal resistance caused by device aging and dust accumulation in the whole life cycle is not taken into account. In order to solve this problem, a flexible equivalent thermal model is proposed to characterize the effect of device aging and dust accumulation, which is updated with life consumption. The life prediction of power devices in continuous operation and actual discontinuous operation under different scenarios is carried out by using the method of measuring the temperature in time segment. The VIENNA rectifier is selected as the front-stage topology of the charging module of 30 k W electric vehicle, and a flexible equivalent thermal model updated with life consumption is constructed. By comparing the life prediction results of power devices in different scenarios, it is verified that the proposed method has higher prediction accuracy.