The purpose of this study is to identify factors for library space programs through user needs assessments in order to apply a library construction. Research method used was a questionnaire and subjects were residents and library users lived in Yongin where a new library was constructing. The results show that library use behavior, age, and user companions are identified as factors to influence to both functional space ratio and functional space arrangement. Reading in libraries is major activity and many subjects went to library with family so that family space is needed. Space for variable ages, also, is needed because of different needs based upon ages.