A brake control system of a rail train comprising multiple vehicles, the multiple vehicles comprising power vehicles and non-power vehicles, the system comprises a vehicle brake control unit, a train brake control unit, a traction control unit, and a communication control unit; each vehicle of a rail train is provided with the vehicle brake control unit; each of the vehicles located at both ends of the rail train is provided with the train brake control unit and the communication control unit; each of the power vehicles of the multiple vehicles is provided with the traction control unit; the vehicle brake control unit, the train brake control unit, the traction control unit and the communication control unit perform communication by means of gateways; the train brake control unit is configured to calculate, according to braking information sent by the vehicle brake control unit and the traction control unit, data of air braking force and an electric braking force to be applied; the vehicle brake control unit is configured to perform air braking on the train according to the data of the air braking force to be applied which is sent by the train brake control unit; the traction control unit is configured to perform electric braking on the train according to the data of the electric braking force to be applied which is sent by the train brake control unit; and the communication control unit is configured to receive a braking instruction from a driver controller, and send the braking instruction to a system where the instruction is executed, each vehicle is provided with a multifunction vehicle bus; each of the vehicle brake control unit, the train brake control unit, the traction control unit and the communication control unit is connected to the multifunction vehicle bus; the multifunction vehicle bus is connected to the gateway; the gateways between the multiple vehicles are connected to one another by means of a wired train bus, characterized in that the train brake control unit comprises a primary unit and an auxiliary unit; the primary unit is the train brake control unit which is provided on the vehicle at one end of the rail train where the driver is located, and the auxiliary unit is the train brake control unit which is provided on the vehicle at the other end of the train; the primary unit and the auxiliary unit are connected to one another by means of the gateway; when the primary unit malfunctions, the auxiliary unit is upgraded to service as the primary unit. the train brake control unit is configured to calculate, according to braking information sent by the vehicle brake control unit and the traction control unit, data of air braking force and an electric braking force to be applied; the vehicle brake control unit is configured to perform air braking on the train according to the data of the air braking force to be applied which is sent by the train brake control unit; the traction control unit is configured to perform electric braking on the train according to the data of the electric braking force to be applied which is sent by the train brake control unit; and the communication control unit is configured to receive a braking instruction from a driver controller, and send the braking instruction to a system where the instruction is executed, each vehicle is provided with a multifunction vehicle bus; each of the vehicle brake control unit, the train brake control unit, the traction control unit and the communication control unit is connected to the multifunction vehicle bus; the multifunction vehicle bus is connected to the gateway; the gateways between the multiple vehicles are connected to one another by means of a wired train bus, characterized in that the train brake control unit comprises a primary unit and an auxiliary unit; the primary unit is the train brake control unit which is provided on the vehicle at one end of the rail train where the driver is located, and the auxiliary unit is the train brake control unit which is provided on the vehicle at the other end of the train; the primary unit and the auxiliary unit are connected to one another by means of the gateway; when the primary unit malfunctions, the auxiliary unit is upgraded to service as the primary unit.