The invention discloses a method and device for detecting the distances between vehicles and belongs to the field of computers. The method includes the steps that a road in front of the first vehicle is photographed to obtain a road image, and an inner lane line of the road is extracted from the road image; according to the inner lane line, the yaw angle between the running direction of the first vehicle and the inner lane line is calculated; whether the second vehicle exists in a lane is determined; if the second vehicle exists in the lane, the first transverse distance and the first longitudinal distance between the first vehicle and the second vehicle relative to the running direction of the first vehicle are calculated; and according to the yaw angle, the first transverse distance and the first longitudinal distance, the second transverse distance and the second longitudinal distance between the first vehicle and the second vehicle relative to the direction of the inner lane line are calculated. The device comprises a photographing module, an extracting module, a first calculating module, a determining module, a second calculating module and a third calculating module. Through the method and device, the accuracy of detecting the distances between the vehicles is improved.