Abstract: Decision Making Models are developed for energy conservation in metallurgicalprocess system,based upon the optimization theory for large systems.These modelsconsist of the multistage Input-Output Model and Decomposition-Coordination Model.Their formulation,algorithm and microcomputer software are explained in considera-ble detail.The models of saving energy in ironmaking process system are describedand discussed as a specific application of process modeling methodology.A reason-able scheme to minimize costs and energy is worked out in ironmaking processsystem.This scheme has yielded good results in saving energy.