The invention discloses an early-warning device capable of tracking a fault at the front end of a vehicle vacuum brake. The early-warning device comprises a body, a front end early-warning signal device (15), a tail end early-warning signal device (19) and an engine rotation speed pulse signal obtaining device (20). The body comprises a shell, a loudspeaker (6) arranged in the shell, and a circuit board (3) connected with the loudspeaker. The circuit board comprises a power source circuit, a control circuit, a voice circuit, a power amplifier circuit and a waveshaping circuit. The power source circuit provides two different voltages for the power amplifier circuit, the waveshaping circuit, the control circuit and the voice chip circuit through voltage reduction. The front end early-warning signal device and the tail end early-warning signal device are connected with the control circuit. The control circuit is connected with the voice circuit and the power amplifier circuit. By the adoption of the early-warning device, the effect that a vehicle has enough time to be processed with effective measures before the vehicle completely loses braking capacity can be guaranteed, safety of a driver and other personnel on the vehicle is guaranteed, and reliability and accuracy of early-warning can be guaranteed.