When trains run at high speeds, the friction power losses within axle bearings are severe under the wheel-rail impacts, especially existing track irregularity and wheel flat. In such situation, the mechanical behavior of axle bearings is seriously affected, which may even induces bearing structural damage, threatens train safety. To analyse and simulate the power loss of axle bearings excited by track irregularity and wheel flat, a numerical model of power loss in axle bearing is posed, with coupled vehicle-track dynamics system. The power loss model synergistically incorporates the dynamic interactions among the bogie system, track system, vehicle-rail relationship, and axle bearings. Further, it also takes into account the impacts of inlet shear heating and kinematic replenishment/ starvation within the axle bearing on power loss. Results indicate that the power loss within the axle bearing is intensified due to track irregularity. Bearing power losses increase as vehicle speed and wheel flat length increase. Additionally, the power loss of the outside row in axle bearing is higher than that of the bearing inside row. The model offers useful mechanism theories for both the structural design and condition monitoring of axle bearings in high-speed trains.