The invention relates to a locomotive car, a control system of a back locomotive car part and a vehicle speed control method. The locomotive car comprises a front locomotive car part and the back locomotive car part. The control system of the back locomotive car part comprises a controller and a power device, wherein the controller is respectively connected with the front locomotive car part and the back locomotive car part so as to acquire the vehicle speed signal of the front locomotive car part and current status of the back locomotive car part as feedback signal, and generate a control signal according to the vehicle speed signal of the front locomotive car part and current status of the back locomotive car part; and the power device is used for driving the back locomotive car part and is connected with the controller so as to control the vehicle speed of the back locomotive car part according to the control signal. According to the invention, the vehicle speed of the back locomotive car part is controlled through the vehicle speed signal of the front locomotive car part and the current state information of the back locomotive car part, thus the reliability, safety and driving property of operation of the whole locomotive car can be improved.