The civil airports now mostly use the imported equipment, the maintenance of electronic circuit board becomes the important segment of aviation electronic equipment maintenance. In the rising and development of component level maintenance, as a new nondestructive testing technology, infrared fault diagnosis gets more research and application. The paper utilizes the Ti50 thermal infrared imager to design a set of electronic circuit of infrared diagnostic system. Considering the real-time and complexity of electronic circuit board, by applying different signal sources, we first group the electronic components of electronic circuit board, then measure, which can rapidly narrow the scope of failure and prevent undetected. Through testing laboratories and the actual use, the speed of the test system is high, diagnostic efficiency is good, with a strong practical value.