The multi-chip insulated gate bipolar transistor (IGBT) module is widely used in high power converters. Condition monitoring is an effective method to improve the reliability of power equipment. This paper proposes a partial chip fault detection method for multi-chip IGBT modules based on the change in turn-on delay of IGBT. Firstly, the in-fluence of chip failure on the turn-on process is analyzed, and the relationship between chip failure and turn-on delay is pointed out. Then, a fault monitoring method is proposed based on this relationship between turn-on delay and number of failed chips, and the effectiveness of the method is verified by experiments. The experimental results show this method has important significance for improving the operating reliability of the converter.