According to the dissipative structure theory, human has much in common with man-made machine, and there is much in resemblance between disease healing of human and fault overcoming of machine. Under the light of the systemics, by introducing the methodology of medical science into the field of machine fault diagnosis, prediction and prevention, it is possible to build a new theory of PME (Plant Medicine Engineering) to prevent and eliminate faults of machine by engineering means. Some common issues, such as the forming of diseases and faults, how to diagnose those diseases and faults, the deep rule concerning the causes and mechanisms of faults and diseases, comparison between curing and self-healing, and between the dealing of symptoms and that of initial causes, etc. , were discussed in this paper. A novel “crystal box approach” of PME, which is based on the piths of both “black-box approach” of traditional Chinese medical theory and uwhite-box approach^ of modern west medical science, was put forth. Lastly, from the view point df PME, some pitfalls in current studies about fault diagnosis are discussed.