Abstract: Vibration and temperature signals from bearings contain rich fault characteristic information, making them crucial for condition monitoring and fault diagnosis of traction motor bearings in heavy-haul locomotives. This study establishes a thermo-vibration coupling dynamics model for heavy-haul locomotive traction motor bearings, based on vehicle-track coupled dynamics. The model considers the nonlinear normal contact and tangential friction effects between the roller, raceway, as well as their defect areas. The influence of raceway defects in motor bearings on the thermo-vibration coupling characteristics of the traction motor is investigated. Additionally, the mapping relationship between defect width and both vibration response and bearing temperature rise is constructed. Results indicate that when the defect width reaches 1 mm, distinct fault characteristic frequencies appear in the vibration signal spectrum. The root mean square frequency, a frequency-domain statistical indicator, shows an increasing trend across the entire defect width range, while the frequency standard deviation is more sensitive to early defects. Time-domain statistical indicators of vibration signals, such as root mean square (RMS) and kurtosis values, are relatively sensitive to outer raceway defects. Conversely, inner raceway defects lead to a rapid temperature increase in the traction motor bearing, which is prone to triggering temperature rise alarms.