Now a days many Interactive Theater research is appeared. We have developed an emotion-based interactive theater system. The characteristic is the use of Interactive Computer Grapfics technology and the generation of three-dimensional imagery to create autonomous actors and a cyberspace in which all participants obtain a feeling of immersion. We have developed a system that includes multi person participation, emotion recognition and gesture recognition through. In this system, participants can feel they are actually contributing to the development of the story in cyberspace. This is done a system that shows avatars on the screen as the alter egos of the participants. We have also produced an interactive story based on this system. We selected "Romeo and Juliet" by Shakespeare as the base story. The main plot of the story is as follws. After their tragic suicide, the souls of Romeo and Juliet are sent to Hades, where they have no recollection of the past. Then, Romeo and Juliet each start on a journey to rediscover themselves and what relationship they shared with their characters, who are emotion-based autonomous actors.