The research is for an interaction of human, activity, context, assistive technology and effect of the result of the playing activity which applies assistive technology from the viewpoint of Human Activity Assistive Technology(HAAT) model. HAAT model offers the basic principle which can use proper assistive technology system on the playing activity of the developmental disability children. Using HAAT model, the study specifies what,where and with whom developmental disability children do by the using of assistive technology. The study explains that the successful playing activity must be accomplished by the harmony of children`s ability and skill. Also, it explains assistive technology facilitate harmonious playing activity. For the effective playing activity, active intervention which applies assistive technology is needed at the children playing activity, and children`s playing environment and the role of parents and therapists for facilitating children`s playing environment is important. Therefore, the evaluation considered interaction of the each component by HAAT model is important for taking children`s playing activity successfully. In further study, the consideration about the using of the tool that can evaluate the children`s playing activity, the effect of assistive technology system and satisfaction after appling assistive technology is needed.