The paper discusses an approach to the question of the possibility of a mathematical description of discrete processes. On the basis of these processes a large class of manufacturing equipment – production lines and systems for the processing of fish was generated. The use of mathematical models in the early stages of the design will improve the efficiency and quality of the produced equipment and reduce the risks and costs during the design work. We propose to describe the processes of fish processing by topological models that are presented in the form of functional graphs. Overall, the proposed approach will develop new design methods of fish processing equipment.