This paper introduces techniques to recommend standardized tags using tag ontology. Tag recommendation consists of TWCIDF and TWCITC; the former technique automatically tags a large quantity of already existing document groups, and the latter recommends tagging for new documents. Tag groups are created through several processes, including preprocessing, standardization using tag ontology, automatic tagging and defining ranks for recommendation. In the preprocessing process, in order to search semantic compound nouns, words are combined to establish basic word groups. In the standardization process, typographical errors and similar words are processed. As a result of experiments conducted on the basis of techniques presented in this paper, it is proved that real-time automatic tagging and tag recommendation is possible while guaranteeing the accuracy of tag recommendation.