This paper proposes an automatic Web services composition method that satisfies the userpsilas request efficiently. Using the method, the available services in a local repository described in OWL-S are translated into a set of production rules, and the dependency rules of the Web services are established using interface matchmaking. We choose reasoning Petri nets (RPN) as the model of this set of production rules. Then we design a Web services composition reasoning algorithm based on the RPN model. The reasoning process of Web services composition is accomplished more simply, quickly, and its efficiency is also improved due to the parallel operation ability of Petri net.