Insulated gate bipolar transistor(IGBT) is one of the key reliability sensitive components of power electronic equipment. Developing prognostic method for defects in an IGBT module is an important measure to enhance the reliability lever of IGBTs. Therefore，a novel prognostic method based on dynamic time warping(DTW) deviations of time series is presented. This method utilizes variations of DTW of gate voltage series caused by defects to estimate if any defect existes in an IGBT module before breakdown. And application value is verified by test results.