Abstract: In order to accurately evaluate the gate oxide reliability of silicon IGBTs and silicon carbide MOSFETs under different electrical stresses and thermal stresses, a high temperature gate bias test equipment was developed, which is capable of measuring pico ampere level gate oxide leakage current in real time. Further,an on-line monitoring function of threshold voltage is integrated into the test equipment so as to better monitor the status of the tested equipment for reliability evaluation and failure analysis. With this equipment, the high temperature gate bias of commercial insulated gate bipolar transistor (IGBT) devices were tested under the same temperature stress and different electrical stresses. The leakage current gradually decreases at the initial stage of the test. The leakage current has a decent positive correlation with the voltage level at the end of the test-the larger the gate bias voltage, the larger the leakage current. Suitable for various kinds of packages, this equipment meets the test requirements of for high temperature gate bias of silicon carbide MOSFETs as well as silicon IGBTs.