The Description Logic, which possesses strong knowledge representation and reasoning capabilities, is the logic basis of the Semantic Web ontology languages such as OWL and OWL-S, but OWL and OWL-S are deficient in the semantic modeling of the dynamic services composition and also do not consider the user preferences in the dynamic services composition. The AI planning, which provides an effective method for solving the planning problem and task decomposition in AI, possesses better modeling capability of the action state transformation, but the AI planning is limited in the knowledge representation and reasoning capabilities. Based on the merits of the Description Logic, OWL-S and the AI planning, this paper extends the OWL-S model, proposes a service composition mechanism and testifies its feasibility in Description Logic. The results show that this composition mechanism can not only be feasible but also be helpful for the semantic modeling of the services composite process in the Semantic Web.