There are a large number of indirect schema mappings between peers in the network. To improve the efficiency of data exchange and queries, indirect mappings are needed to be composed. Direct mappings can be derived directly by the constraints defined between schemas, but not for indirect mappings’ composition. Defined the combination operations of schema elements in indirect mappings, and gave the expression of indirect mappings. Analyzed the composition of indirect mappings, and proposed a strategy, named schema element back, to solve the problem of indirect mapping composition, and gave the indirect mapping composition generation algorithm based on such strategy. Experiments showed that indirect mapping composition can improve the efficiency of data exchange, and compared with other non-full mapping composition generation algorithms, and indirect mapping composition generated by our algorithm based on schema element back strategy can completely eliminate the infection of media schema with no reduction of the composition efficiency.