This paper presents the unique formation process of a volumetric space with the digital algorithm developed for Voronoi diagram in order to generate an effective parametric architectural form. By applying systematic parameters of architectural conditions within digital parametric tools, the interactions among sub-spaces developed by Voronoi diagram are enhanced by manipulating the spatial structures. In this paper, we discuss how the parametric distributing and zoning geometrical system can support designers in developing a free-formed space, and research on how this system creates a 3D volumetric space. With the in-depth research on the system and structure of Voronoi diagram, the approaches to the application of Voronoi diagram into architectural form generation are clarified to be an effective, creative and successful digital tool. The result of the application of the Voronoi diagram improves the design quality with systematic language in the sense that the sub-regions are created and controlled under the systematic and balanced hierarchy having dynamic relationships among each others with the restoration of the equilibrium of forces and tensions. This 3-dimensional Voronoi diagram provides another means for designers to solve architectural issues and to reinforce their design concepts.