The invention belongs to the technical field of automobile active safety, and particularly relates to a tracking and predicting device of the motion state of a front vehicle and a predicating method thereof. The tracking and predicting device of the motion state of the front vehicle comprises the vehicle, an ARM9 processor, a camera fixed to the center of the outer side of the front windshield of the vehicle, a lane line sensor for detecting the position relation between the vehicle and a lane line where the vehicle is located, a vehicle speed sensor for collecting driving speed data of the vehicle and a millimeter-wave radar for emitting signals to the position in front of the vehicle; a lens of the camera faces the position in front of the vehicle; the lane line sensor is fixed to the center of the outer side of the front windshield of the vehicle; the millimeter-wave radar is fixed to the outer side of an air inlet grating of the vehicle; the signal input end of the ARM9 process is electrically connected with the signal output end of the vehicle speed sensor, the signal output end of the lane line sensor, the signal output end of the camera and the signal output end of the millimeter-wave radar.