Abstract: In order to solve the problem of non-uniform running speed of collagen casing production line, length change before and after retraction, and error caused by the lack of identification marks in cutting position of the cutter, a new collagen casing length detection method, spraying mark detection, was used, and a set of high-precision photoelectric detection system was designed to cut the fixed-length collagen casing. Based on microcontroller unit TM4C123GH6PM and using electro-optic rotary encoder, inkjet printer and digital color-sensing fiber sensor as the main devices, and utilizing the casings stretching facility in factory, the system makes the theoretical and experimental verification during the process of the cutting fixed-length collagen casing. The results show that the measurement accuracy of casing reaches 0.1mm, and the error cutting reduces from ±0.3m to ±0.05m. The average cost of produce for each casing can be reduced by 4%. The photoelectric detection system is suitable for industrial applications and can greatly enhance the competitiveness of enterprises.