[en] High construction technologies enable huge underground structures and a number of new structures are constructed underground over the limit. Construction of underground structures increases available surface space and resolves many specially-considered problems of onground structures, which increases safety and reliability of structures. Since a slight accident of a nuclear plant can bring a catastrophe, however, application of new construction technologies is required to be careful. In this study, strengths and weakness of underground nuclear plants are examined and compared with those of on-ground nuclear plants. Three fundamental concepts of seismic deformation method, response acceleration method, and dynamic analysis method for seismic response analysis of underground structures are reviewed. Korean seismic design code for underground cavity is summarized. The underground nuclear plants have strengths such as upgrade of containment, improvement of seismic safety, economic benefits, and ease of decommission. However, a few studies have been performed about the underground nuclear plants. They are not studied in Korea. Since importance of the underground space is increasing in Korea which has limited surface space and underground nuclear plants will be constructed in the near future, strong theoretical and technical foundations has to be provided through detailed studies on the underground nuclear plants