The utility model provides a car automobile lamp mask size measurement device based on optical scan mirror, its characterized in that: including six roots of sensation anchor post 1, six roots of sensation anchor post is with regular hexagon evenly distributed, regular hexagon center and test position center coincidence, install capable of vertically moving's regulation crossbeam 2 on every spinal branch post, install a laser instrument 3 on every crossbeam 2, 4 and two CCD cameras 5 of a miniature scanning mirror, the central line of optical scan mirror 4 drops on the intermediate position of being surveyed automobile lamp mask, the relative pillar with the laser instrument of digital micro scanning mirror center bilateral symmetry on every crossbeam places, the miniature scanning mirror and the laser instrument outside are arranged in with specific contained angle respectively to CCD camera about 5. Compare with the contact measurement device, the utility model has the characteristics of easy and simple to handle, the precision is high, can satisfy all kinds car automobile lamp mask 's size detection requirement.