The invention relates to a fault case library, a fault tree and a fault spectrum construction method. Firstly, an efficient multi-level state detection data comprehensive index model is established, and test data are modeled from multiple dimensions. The intellectualization research of expert experiences, case libraries and rule bases is developed, and diagnosis techniques and multi-information fusion techniques based on various types of standardized state detection data are used for improving the accuracy of analysis and diagnosis. Secondly, construction techniques of standardized and intelligent typical fault case libraries are studied on the basis of fault case libraries and related relational libraries, and then the fault tree and the fault spectrum are constructed based on the fault case. Finally, a typical case library for on-site operation and maintenance of transformer equipment is constructed. The method can effectively ensure that power equipment operates under normal conditions, and can detect and eliminate the malfunction of the power equipment in time by detecting the data, the specialization and intelligence level of the on-site operation and maintenance is improved,the efficiency of transportation inspection and management and control capability for equipment status are improved, and status overhaul and assist decision-making are strengthened.