Abstract: Based on the complete decomposition model of energy consumption intensity，the factors which caused the changes of energy consumption intensity for iron & steel industry in China were decomposed into structure effect and efficiency effect. Thus, the decomposition model of energy consumption intensity for iron & steel industry was established. The changes of energy intensity was quantitatively analyzed based on the data of1980-2004. The following results are achieved: the mayor factor changing energy consumption intensity for iron & steel industry was the efficiency effect whichwascaused by technological progress, while the structure effect had a negative impact on the energy efficiency.