with the rapid development of web 2.0 technology, more and more social annotation systems are emerging, such as del.icio.us, flickr, youtube, and citeulike. these systems help users to manage and share their digital resources, and have attracted a lot of users to annotate the resources with tags and bookmarks, which result in a large scale of tag data. due to the exponential increase of social annotations, all the users are facing the same problem: how can we explore the desired resources efficiently in such a large tag dataset? since the traditional methods, such as tag cloud view and annotation, match work well only in small annotation dataset, this paper studies the relationships of tag-tag, tag-resource and resource-resource through the co-occurrences and proposes a new efficient way for users to organize and explore the literature resources. our research mainly focuses on two aspects: 1) the hidden semantic relationships of popular tags and their relevant literature resources; 2) the computing of literature resources similarity given a specific literature. a prototype system named pkuspace is implemented and shows promising results.