The present disclosure provides a gearbox of a rail vehicle, which belongs to the technical field of gear transmission. The gearbox of the present disclosure comprises a driving shaft, a driven shaft, a first bearing seat and a second bearing seat; the gearbox further comprises: a first roller bearing, a ball bearing, a bearing inner retaining ring and a bearing outer retaining ring for drainage, which are arranged between the first bearing seat and the driving shaft; wherein, the bearing inner retaining ring and the bearing outer retaining ring are provided between the first roller bearing and the ball bearing along an axial direction of the driving shaft, and a first drainage channel is provided on the bearing outer retaining ring, a second drainage channel is provided on the first bearing seat; wherein, the lubricating oil can be guided into the first roller bearing and the ball bearing from the outside of the first bearing seat through the second drainage channel and the first drainage channel in sequence. The present disclosure can greatly improve the lubricating performance of the first roller bearing and the ball bearing on the driving shaft of the gearbox, and is particularly suitable for low-temperature working conditions.