Traditional Open Directory Project (ODP)-based text classification methods use bag-of-words approach, which only utilizes single words in ODP documents and ignores important types of semantic information such as phrases and related terms. In this paper, we propose a method for enriching the semantic information in ODP documents by utilizing Wikipedia knowledge. First, we construct a phrase dictionary based on Wikipedia and search for Wikipedia phrases in ODP documents. Second, we select the most likely relevant Wikipedia articles and relevant hyperlinks for Wikipedia phrases in ODP documents. Finally, we add Wikipedia phrases and relevant hyperlinks to ODP documents to enrich the semantic information. Our evaluation results verify the efficacy of the proposed methodology.