This article deals with the problems related to the elucidation of the structures of the mechanisms in multifunctional catalytic systems (MFCSs). Graph theory can be used to classify these mechanisms. The elements of the mechanisms are circuits (cycles in the subnetwork of intermediates of a mechanism). A circuit can be (1) balanced, when it has a unique overall equation that characterizes the catalytic function of a circuit, or (2) unbalanced, in which case it has no unique overall equation. The structure of MFCS may be characterized by the list of circuits in the subnetwork of intermediates and a special graph that reflects specific relations between steps, circuits, and their catalytic functions. The equivalence classes of these graphs may play the role of a feature that classifies MFCSs. Examples of MFCSs are considered for various mechanisms in the catalytic systems of metal complexes.