Abstract: Photocatalysis is one of the most ideal technology to solve the energy and environmental problem, which could make use of sufficient solar energy to decompose water to H₂, degrade various organic pollutants, and reduce CO₂ to organic low-carbon fuel.The present infrared spectrometer can only be used to analyze the molecular structure of photocatalytic materials in a conventional manner, which cannot investigate the illumination process in real time, and cannot realize the real-time detection and characterization of the change of photocatalytic material and reaction mechanism during the illumination process.An in-situ infrared spectroscopic cell system for the photocatalytic materials has been designed to provide a real-time detection and characterization of catalytic materials during the illumination process, so as to analyze the reaction mechanism of in-situ infrared photocatalysis and realize the real-time detection and characterization of the reaction mechanism of photocatalytic materials.The system provides a strong technical support to study the real-time structure change of photocatalytic materials, and is a very important technical innovation for the functional development of infrared spectrometers.