As the rapid develoment of internet and information technology, the traditional library has been altered to the digital content service based on the world wide web. This paper proposes a design and implementation of an Artcle Union Catalog System(AUCS) based on metadata. The metadata set for the AUCS consists of twelve Dublin Core elements and one holdings element. The qualifiers of the proposed metadata elements are also represented. The AUCS system has an online cooperated cataloging system using the web interface or the 239.50 protocol, an union cataloging management system, and an integrated information retrieved system service. The integrated search and retrieval service of the AUCS displays not only the summary and detailed bibliographic information, but also the abstract, the table of contents, the digital content, and the copylfax service.