Purpose -The brake connector of an automobile is one important part in the brake system. How to measure the matching surface quality is a problem, because the matching surface is a cone surface and has a deep aperture structure. Design/methodology/approach -A new measurement system is presented which could assure illumination and image with a special beam splitter. The worker could observe the matching surface by better image. Findings -More objective evaluation is given with image processing method. Research limitations/implications -Now, this measurement system is used by Toyota (Tianjin) company and satisfied result is obtained. Originality/value -This paper is an original work and focuses on an important issue in automobile production.