Efficient search in decentralized peer-to-peer systems is a challenging problem. An intelligent search mechanism based on topology evolution, named ITSON, is proposed. Each peer clustered with peers in similar interests into a community and chose important communities as logical neighbors based on the past queries. For a new arriving query, the most possible communities that have the query answers were selected according to topology evolution to send the query. With queries done, overlay network topology can be adjusted automatically with little cost. Simulations reveal that ITSON greatly improves the search efficiency and guarantees the search effectiveness.