For 3D story composition, interactive controls such as scene composition, character actions, and camera placement are important processes. In this paper, a Mixed Reality based interactive tool for 3D story composition is introduced. Using the proposed tool, non-experienced users composed 3D scenes through interfaces in his/her real environments. Preliminary studies showed that proposed 3D story composition tool was convenient and useful by interactively updating scenes through user’s control over the stage items and camera viewpoints.