The invention discloses a KNN-based text classification method which is suitable for nuclear safety software verification and reliability verification. The KNN-based text classification method comprises a training process processing step and a test process processing step: representing training sample data sets by information of original texts and all the titles in the texts; and constructing two DBM models according to characteristic hierarchical structures in the texts from shallow to deep, extracting and storing deep characteristics with low dimensionality and high discrimination, and determining the categories of to-be-tested texts through considering the contribute brought from text titles to the similarity calculation via proper weights in the test process. According to the method disclosed in the invention, information of the text titles are fully utilized, the classification performance, relative to the condition of taking the shallow characteristic vectors as training sets, is remarkably improved, and meanwhile, the storage demand and online calculation amount are reduced at the same time, so that the problem of characteristic vector high-dimensionality disaster is solved and the classification correctness is improved; and the method can be used for the matching of rules in safety level software reliability evaluation analysis and the establishment of a failure mode library.