Power loss monitoring is an important approach to ensure the reliable operation of semiconductors and equipment. Accuracy and timeliness of evaluation cannot be fully balanced by conventional methods. This paper addresses the above challenges and presents a new power loss observation method based on augmented Kalman filter(AKF). Based on the measurement of temperature at the edge of the power module, it can realize accurate estimation of power loss in real time. The effectiveness of the proposed method is validated by the experiments.