Limited by the camera''s field of view, the truck contour dimension measurement based on machine vision cannot obtain a complete body image at one time. Therefore, image stitching technology is introduced on the basis of traditional machine vision measurement, and a dynamic non-contact measurement method of truck size is designed, which can be used for feature extraction, image registration and fusion, and external contour dimension measurement of sequence truck images without stopping and contacting. Simulation results show that the average measurement error of this method is 0.83%--1.87%, which meets the requirement of GB21861-2014.