The invention discloses a warning system preventing vehicle tailgating and a warning method, and relates to the field of vehicle safety. The warning system preventing vehicle tailgating is arranged in a vehicle to be used for preventing vehicle tailgating and collision to trigger a traffic accident, comprises a speed and distance obtaining module, a central control unit and a warning module, wherein the speed and distance obtaining module is used for obtaining realistic vehicle speeds and a realistic vehicle distance of the vehicle and a rear vehicle; the central control unit is used for receiving vehicle speed and vehicle distance information of the vehicle and the rear vehicle, calculating a corresponding safe distance according to the information and simultaneously judging whether the realistic vehicle distance is bigger than the safe distance or not; the warning module is used for giving a warning instruction according to a judging result of the central control unit to warn drivers of the vehicle and the rear vehicle to notice to control the vehicle speeds and steering to prevent vehicle tailgating. The invention further discloses the corresponding warning method. According to the warning system preventing vehicle tailgating and the warning method, the drivers can be warned to corresponding measures in advance when the distance between the two front and rear adjacent vehicles is over short and a tailgating and collision risk exists, and thus occurrence of the tailgating and collision accident is avoided.