Abstract: To improve the speed and correctness of Web service matching for services composition process, a semantic matching mechanism is proposed with the help of services indexes. Based on indexes mechanism and services semantic matching algorithm for single service, a composition-oriented services semantic matching algorithm is proposed and the matching usability of service input/output is analyzed. To improve the accuracy of service matching, the semantic matching degree for services category matching is introduced, and then the computation method of overall semantic matching is provided. Experimental results show that this composition-oriented service semantic matching can enhance the efficiency of services matching based on services index.