This paper presents a new method of calculating the sematic similarity between articles based on WordNet. To further improve the performance of the proposed method, we build a new Compact Concept Ontology (CCO) from WordNet by combining the words with similar sematic meanings. The experimental results show that our approach significantly outperforms a recent proposal of computing semantic similarity, and demonstrate the superiority of the proposed CCO method. Categories and Subject Descriptors H.3.m [Information Systems]: Miscellaneous General Terms Algorithm, Experimentation, Performance Keywords Concept, Ontology, Similarity