Since interactive systems that the user interaction is important factor can be very complex, its design process may have various testing and feedback based on continuous prototyping. The prototypes in this process function as medium to explore design problem and communicate opinions with another expert of project team. So prototyping strategy may be needed to enhance the design quality by focusing on the goals of project. This study clarifies critical issues around the prototypes and characteristics of interactive system to understand broad meaning of prototypes. And prototype model proposes as a framework for establishment of prototyping stategy.