Due to the inevitable wheel polygonal wear in operation and the increasing running speed, the service operation environment severely challenges the safety and reliability of gear transmission bearings. To investigate the dynamic responses of bearings excited by wheel-polygonal wear, a vehicle–track coupled dynamics model with gear transmission systems and its bearings is developed. In this model, the nonlinear factors, such as gear mesh stiffness, gear backlash, bearing nonlinear contact, and frictions between bearing roller and raceways, are comprehensively considered. This model has the advantages of analyzing the dynamic behaviours of gear transmission system and evaluating the dynamic responses of the bearings in the coupled mechanical systems. The model is validated by the field test data, and the wheel polygonal wear data is also obtained by field test. Using the dynamics model, the influence of wheel polygonal wear on the dynamic responses of gear transmission bearing in traction condition is analysed and discussed. It indicates that the wheel polygonal wear increases the dynamic interactions within all bearings, and can’ be ignored in the dynamic related research.