The degradation of the power semiconductor gate oxide layer has a serious impact on its normal operation. Different bias stress lead to different forms of gate oxide degradation. Therefore, the condition monitoring research of the gate oxide layer is of great significance to power semiconductor’s high reliability. Starting from the microscopic mechanism of gate oxide degradation, establishing an accurate function relationship between related characteristic parameters and gate oxide degradation. When the gate oxide layer is degraded, the drift of the characteristic parameters can be detected to realize the condition monitoring of the power semiconductor gate oxide layer. Focusing on the domestic and foreign research on degradation characteristic parameters and degradation models, the latest progress on condition monitoring methods based on threshold voltage and Miller effect parameters are discussed in classification, and the performance of gate oxide condition monitoring methods are analyzed and compared. On this basis, combined with the development and application trends of power semiconductor, the research direction of gate oxide condition monitoring of power semiconductor devices is prospected.