The cut set analysis of fault tree is a common technique for judging accidents. However, the technology based on cut sets can only determine the occurrence of accidents by combination of basic events, and cannot analyze the intermediate events in the process of accident evolution. In view of the mechanism of accident analysis described in the accident analysis report, a precise classification method of accident report oriented fault tree is proposed by combining the text classification and fault tree analysis technology, and the accurate classification technology of accident oriented accident evolution path is realized, and the information of the report and the fault tree structure evolution information can be automatically correlated. We can achieve precise analysis of accident causality evolution based on expert experience.