Abstract: There are some faults of present community detection algorithm, which is based on the in degree, out degree and betweenness of nodes,we presented a algorithm based on Entropy to detect community structure. A community ineludes many information and it's Entropy. Members of a community have some common gains or interests, we think that if a member want to join a community, it can't make the entropy of the community exceed a threshold, otherwise it can't be the member of a exist community. Our experiments show the processing and the efficiency of our algorithms.

Key words: Community detection, Information entropy, Recommendation system, Data mining