As domestic industrial endoscopes are only limited in sample observations and can not measure the three-dimensional shapes of workpieces, this paper designs an industrial endoscope whose probe has an outside diameter of 6 mm and is bendable in any directions. It introduces the endoscopic binocular optical system and the endoscopic internal structure. First, a new type of binocular optical system with a dual objective lens and a single image sensor was proposed based on the binocular stereo imaging principle. Then, the endoscopic head structure was designed according to the technical requirements of optical system. In consideration of the complex internal structures of some workpieces, a bendable structure and a back-end control device of endoscope were respectively designed to facilitate detecting precision parts, and the working principle of two structures were described. Finally, the length of two feature points on the surface of target was measured by the three-dimensional image processing software to obtain the distance between the two points. The experiment shows that the length measurement error of the two feature points is within ±0.2 mm. It basically realizes the three-dimensional measurement function of the industrial endoscope systems.