Ubiquitous computing technology provides anytime and anywhere accessibility to information, ubiquitous computing is adapted in the various field to increase efficiency of work. After looking into the trend of ubiquitous computing, case studies of information service using mobile service and RFID system in library were investigated in this paper. Library information service are providing retrieval of library OPAC and verifications of circulation and return date using mobile internet technology. In addition, various notice services using short me sage service(SMS) of mobile are available. Considering growing mobile service and RFID system advancement of related technology, more information service utilizing mobile service and RFID system should be developed in near future.