Abstract: Because the measuring result of azimuth for automobile headlamp beam is prominently influenced by the longitudinal bias angle of the automobile location, a correction method for measuring error was proposed based on digital image processing. Camera was used to take the image of the automobile location. The profile of the automobile’s figure was obtained with the OTSU adaptive threshold segmentation algorithm. The automobile longitudinal bias angle was figured out by the successive approach method. Finally, the measuring result of headlamp tester was corrected by the bias angle so that automatic correction is realized. The experimental results indicated that this method could effectively obviate the influence of the bias angle, and greatly improve the measuring precision of azimuth for automobile headlamp beam.