Overheat fault atlas identification of power equipment is an important tool for judging the fault degree of power equipment. In engineering practice, thermal photography of substation equipment and manual screening are usually carried out. To improve the heat equipment’s figure fault decision accuracy and efficiency according to the characteristics of the three-phase power, this study proposes an automatic search determination method; this method involves the use of the three-phase partition piece temperature contrast of overheating area to separate every figure of the three-phase equipment heat, adjustment of images of similar size and attitude, comparing the new image block, and determining whether there is a corresponding block of abnormal temperature rise to identify the thermal faults of certain phase equipment. The test results show that the equipment thermal diagnostic method based on computer automatic search and determination can identify the thermal fault of three-phase equipment more efficiently and accurately, which improves the efficiency, accuracy, and automation degree of thermal fault detection of power equipment.