The machine vision examination technology which can achieve the engineering products zero waste product production goal， has so many merits such as the non-contact， online real-time， the speed to be quick， the precision is appropriate， scene antijamming ability strong and so on. This technology which adapted the modern manufacturing industry progress and the development request has demonstrated the broad application prospect in reality. This article unifies the machine vision technology and the imagery processing technology. the goal of this article is to realize the automobile length examination and overcomes traditional the manual examination malpractice. This article has developed face the length examination machine vision system's research work， which realizes image adjusting using the gamma transformation and two step projection and realizes the characteristic point extraction using the gradient examination algorithm， Hough transform technologies and integrates image gathering card's principle to realize the automobile length survey at last.
