An assembly for supplying electric energy to a rail vehicle has a wheel set shaft on which two working wheels are arranged without relative rotation, the working wheels rotating around a rotating axisof the wheel set shaft during operation of the rail vehicle and rolling on two traveling rails of a rail path, and a transmission device shell through which driving force generated by a drive motor is transmitted to the wheel set shaft during operation of the rail vehicle, the wheel set shaft can rotate around the rotating axis to support through a first rotating bearing fixed on the transmissiondevice shell, the transmission device shell is arranged in the manner of being staggered from a middle position, the middle position is located in the middle at the same intervals from the working wheels, a pipe is fixed on the transmission device shell, the pipe extends from the transmission device shell to the middle position, the wheel set shaft extends to pass through internal space of the pipe, and a current collector is fixed on the outer side of the pipe, so as to realize electrical contact with a third rail arranged to be used for supply energy to the rail vehicle and conduct currentto the rail vehicle during operation of the rail vehicle.