Abstract: To improve the level of thermal fault diagnosis for electrical equipment, this article constructs a thermal fault diagnosis system based on red thermal imaging technology and elaborates on the application points of this technology. By understanding the types and classification methods of thermal faults in electrical equipment, this paper explores the specific points of infrared image thermal fault diagnosis. Based on theoretical analysis, a 220 kV substation in an industrial intensive area of East China is taken as an example for case analysis. Infrared image technology is used to diagnose thermal faults in isolation switches, wiring joints, and high-voltage bushings. Based on the results of thermal fault diagnosis, processing methods are proposed to ensure the stable operation of electrical equipment.