Abstract: Traction motors are essential components of the train's drive system, providing power for train operation. Long-term operation under variable speeds, high loads, and high-temperature environments has exacerbated the occurrence of traction motor failures. Once a traction motor fails, it poses a threat to train operation safety. Therefore, conducting fault diagnosis research on train traction motors is of great significance. This paper first introduces the classification of traction motors and common types of train traction motors. Then, it summarizes different kinds of faults based on the common locations where traction motor faults occur. Next, it reviews the research achievements of domestic and international scholars in traditional fault diagnosis and machine learning-based fault diagnosis. Finally, it summarizes and prospects for the development trends and future research directions of train traction motor fault diagnosis technology.