The steam system in petrochemical plants is composed of steam under various pressure levels. The imbalance between the demand and supply of steam at various levels generally exists, which causes large amount of steam transformed from the upper level to the lower one through the temperature and pressure reducing valves, and abundant low-pressure steam. Both of them result in the degradation loss of energy. In order to improve the steam system and to reduce the energy degradation loss, this paper analyses various situations of steam mismatch at different pressure levels by the Grand Composite Curve. By using the adjustable range of steam turbines as boundaries, the operation improvement and specific retrofit schemes, such as using steam turbines, steam ejectors, or absorption refrigeration, have been proposed to show the improvement opportunities for matching the demand and supply of steam at each level.