The main purpose of the study is to find the code with similar possibilities to effectively avoid the adverse effects of code duplication. Through the clustering pretreatment of document feature information, to extract the relevant features of the document. Then the basic characteristics are used to cluster the document, to find out the best number of clusters. According to the reasonable number of clusters that have been found, using the vectors that generated through TF-IDF method, combined the K-means clustering algorithm to distinguish the contents of the files, as well as the introduction of cosine similarity, to determine the similarity of two texts and classify the parallel documents. From the test data set, the method can accurately find the code with the possibility of duplication and works quiet well.