An ontology for Semantic Web Services is proposed in this paper, whose intention is to enrich Web Services description. Distinguish from the existing ontologies, the proposed ontology is based on both functionalities and performances, and it is organized as a layered construction. The discovery related with the proposed ontology is also discussed. Based on the Service Oriented Architecture, the proposed ontology is helpful for requesters to find their suitable services according to their own preference. Besides, as an example, an ontology for the learning resource is organized in the paper.