The invention discloses a cracked porcelain insulator judgment and diagnosis method based on a decision tree. The method comprises the steps of (A) taking pictures of insulators and carrying out image recognition to distinguish different insulators, and (B) analyzing the temperature values of different insulators in the images, arranging the temperature values, and forming a characteristic value matrix to carry out decision tree judgment to identify a cracked insulator. According to the method, the shortcomings of the prior art can be improved, a phenomenon of wrong detection of a normal piece and missed detection of a cracked piece in the infrared detection process is reduced, the accuracy of cracked porcelain insulator detection is improved, a large number of infrared images can be accurately and effectively processed in the inspection process, and the cracked piece is found.