The Foundations of he Semantic Web’s logic is Ontology. The main purpose of that research is to extend the current Web in order to make the information in the network have its semantic understood and handled by the computer. The main purpose of the Semantic Web research is to solve the problem which people and computer can understand and handle the knowledge. So, the inference services base on the semantic Web can be developed. In this way, firstly analyzed the base of the semantic Web, and then we researched the inference of semantic Web, At the end, a reasoning system base on this research is proposed. The reasoning system solves some problems that are brought by the traditional knowledge representation, and sharing knowledge is easy.