Industrial optical fiber endoscope is a kind of remote visual inspection equipment, with fine diameter, flexible characteristics, mostly used for some narrow curved test piece internal inspection, such as: turbine, small diameter process pipeline, aircraft fuselage, boiler pipeline maintenance, easy to use, is widely used. Understanding the imaging principles of industrial fiber optic endoscope can help to buy good products. Industrial fiber optic endoscopes often consof the objective lens, the mirror tube, the control unit, and the eyepiece. The guide beam providing lighting and the guide fiber optic beam responsible for transmission are all running through the mirror tube. The imaging core of optical fiber mirror lies in the optical fiber beam, and its imaging principle can be understood from the perspective of local single optical fiber and overall optical beam.