We consider one of the classes of hybrid systems, heterogeneous discrete systems (HDSs). The mathematical model of an HDS is a two-level model, where the lower level represents descriptions of homogeneous discrete processes at separate stages and the upper (discrete) level connects these descriptions into a single process and controls the functioning of the entire system to ensure a minimum of functionality. In addition, each homogeneous subsystem has its own goal. A method of the approximate synthesis of optimal control is constructed on the basis of Krotov-type sufficient optimality conditions obtained for such a model in two forms. A theorem on the convergence of the method with respect to a function is proved, and an illustrative example is given.