Abstract: One foundation of the semantic Web is ontology—to make Web contents understandable to machine and suitable for inference, ontology needs to be established, and the Web contents should be annotated with metadata which are defined as terms in ontology. The relation between ontology and domain ontology is explained; the overview of ontology languages for the semantic Web is introduced; based on trade-off between expressivity of knowledge and complexity of reasoning problems, OWL Lite is selected as ontology language; then DORRSW (domain ontology representation and reasoning for the semantic Web) and MDOISW (multiple domain ontology integration for the semantic Web) are proposed; Finally DORRSW and MDOISW are applied to solve an example problem. From these discussions, the basic situations of domain ontology representation, reasoning and integration for the semantic Web are clarified, so the basic knowledge of developing ontology for the semantic Web is provided.