The interior of CNC machine tools is relatively precise and the overall structure is very complex. It is a relatively advanced mechanical equipment and is widely used in some relatively large factories. In today’s society, various industries are using intelligent diagnostic technology, which is developed on the basis of computers and artificial intelligence. Because the process of fault diagnosis and processing of CNC machine tools is very cumbersome, the development of diagnosis technology is also becoming more and more intelligent with the development of the CNC industry, which provides a strong guarantee for ensuring the safety of machine tools. In CNC machining, intelligent detection technology also plays an increasingly important role. The intelligent diagnosis system of CNC machine tools is to apply artificial intelligence technology to the CNC system. This paper summarizes the types of CNC machine tool faults and explains in detail the characteristics of CNC machine tool fault diagnosis. Diagnose and repair, thereby reducing economic losses. Finally, this paper looks forward to the main research directions of the future intelligent fault diagnosis technology of CNC machine tools.