The process system design is a very creative work. The purpose of this paper is application of process vectors to this creative activity. There are two process groups in the system. The first group generates a special function to produce the target material or energy, and hence it is called a functional structure. Graphical presentation by process vectors may give us intuitive suggestions for creating such a functional structure. The second group is generally composed of an energy-donating process and an energy-accepting process. Here the process vectors are applied to representation of the features of energy transformation between them and the exergy loss caused by this transformation. By drawing those vectors on a process flow diagram, we can represent characteristic features of an entire process system on a single diagram.