This paper presents the methodological basis for creating a model system for selecting the optimum composition of blast furnace burden, providing the required technical and economic performance and the melting of pig iron of the required composition. The system implements a new systematic approach to modeling the processes of directed formation of blast-furnace melts. Description of composition and properties of metallurgical systems in different states is based on an original concept of directional chemical bonding using integral parameters of interatomic interaction of components in the system. The developed complex of mathematical and physical-chemical models and criteria provides a solution to the direct problem of predicting the composition of pig iron and properties of blast furnace slag, depending on burden and technological conditions. Determination of the optimal burden composition is carried out using vector optimization methods with mandatory verification of compliance with the technological requirements of high-temperature properties of the burden. The results of testing the model system on actual industrial data of blast furnace operation are illustrated, which made it possible to formulate recommendations on the composition of the loaded feed, taking into account the available raw material and energy resources.