Abstract:A method to monitor the examination object diameter based on the infrared technique is showed. Through regulate the system accuracy, it can realize auto controlmonitor and the examination diameter bigger than 50μm. The workflow and main function models in the design is introduced. The system is suitable for actual application environ-ment such as textile, machine, food equipments, etc. It realizes the control of quantity examination of production inline, and has characteristics of stable rapid and high precision.