In this thesis we develop a 3D soft object modeling system with implicit functions. Our system provides implicit functions including the primitive functions and blending functions to modeling soft object. The system satisfies some requirements, such as intuitive operating environment, the Model-View-Controller (MVC) system architecture, and extensibility, etc. The system consists of four major parts: (1) the graphical user interface (GUI); (2) the constructive tree viewing Subsystem; (3) the implicit function operating Subsystem; (4) the 3D scene graph rendering Subsystem. The GUI initializes the window frame and responds to the event messages dispatched from the OS or applications. The constructive tree viewing Subsystem presents the composition of the object modal with the tree structure. The implicit function operating system accomplishes the polygon tessellation, that is, it translates the blending tree with the implicit functions to polygon meshes. The 3D scene graph rendering system renders the polygon mesh and provides 3D scene graph manipulations.