Semantic technology has a significant contribution to the service composition. Services coming from providers can be classified with semantic annotations and placed in the specific ontology classes, which accelerates the understanding procedure for machines to quickly decompose coming requests and locate classes accurately for service composition. However, semantic annotations for services in traditional logic may ignore inner connections between classes, which will reduce the amount of potential solutions and chances to advance the performance of the composition. Here we present our Partial-Equivalence logic in service composition, we propose an algorithm to detect the inner connections between ontology classes and enrich the annotation. Then we update the model of the workflow and operate a comparison on the performance of our Partial Equivalent compositon against traditional composition. Our experimental results show that the Partial-Equivalent logic not only offers more solutions to the request, but also simplifies the workflow and advance the performance of solutions. We anticipate that our Partial-Equivalent logic may enrich the tradition logic of semantic annotations and have broad applications in optimizing service composition.