This paper treats a 3D graphics software development system called IntelligentBox and its aspects as a rapid construction system for interactive 3D games. Especially, the author introduces its new aspects as a development system of SaaS (Software as a Service) applications including web-based 3D games. IntelligentBox provides various 3D software components called boxes each of which has a unique functionality besides a 3D shape. IntelligentBox also provides a dynamic data linkage mechanism that allows users to develop interactive 3D graphics applications only by combining already existing boxes through direct manipulations on a computer screen without any text-based programs. This is main feature of IntelligentBox. Application fields of IntelligentBox include 3D animation creation, virtual reality software development, 3D interactive simulator development and so on. Besides them, using IntelligentBox, it is possible to develop interactive 3D games. However, developed 3D games can not be available on WWW. If developed 3D games can be available on WWW like SaaS applications, the usefulness of IntelligentBox would become higher. So, the author extended the IntelligentBox system to make it work as a SaaS application, and then it has become possible to develop web-based 3D games as SaaS applications using IntelligentBox.