Abstract: A new mechanism of resolving data incompletion is presented in this paper. By adding new knowledge in local sites, which is a set of rules expressing the values of unknown attributes using the values of known attributes, a distributed information system is transformed into a distributed knowledge system, and the question is resolved by cooperation among multi sites. A new architecture of the cooperation knowledge based system is also discussed, and the content and construction method of the knowledge level are described. Finally, a cooperation algorithm of processing query is given.