A method includes storing documents of different fields, and a relationship between any two documents of different fields, performing word segmentation and stop word removal on the documents of different fields, to obtain a vocabulary data set for the documents of different fields, constructing an incidence matrix between the documents of different fields according to the relationship between the any two documents of different fields, obtaining a topic cluster of the documents of different fields according to the vocabulary data set, obtaining a probability that any topic in the topic cluster appears in any document and a matching weight of the any topic for any two different fields according to the incidence matrix and the topic cluster, and computing a similarity between the any two documents according to the probabilities and the matching weight of the any topic for the fields to which the any two documents belong.