Energy management system (EMS) will be one of energy-saved technologies for iron and steel route. The paper analyzes EMS structure and development focusing on the energy forecasting, optimization and other key technologies in iron and steel works. Taking gas management subsystem of EMS as an example, the forecasting and optimization are described. Byproduct gas is one of important energy medium in energy system, which can play a significant role in energy savings in iron and steel works. In this paper, the models of byproduct gas generation, consumption prediction and optimal utilization are developed for predicting and distributing byproduct gases to make them emit zero. The results show that: EMS should have hardware and software technology conditions to exert its functions; Energy medium, such as byproduct gas and steam, prediction and optimization will be play an important role in energy conservation and emission reduction.