Based on the data from a steel company, this paper applied life cycle assessment and GaBi 4.3 to analyze the material, energy consumption and emission during production of 1 t on steel by CML2001 method was used to perform environmental impact assessment of steel production. The results showed that the major environmental impact of BF-BOF steelmaking process includes aquatic ecotoxicity, human toxicity, fossil energy depletion and mineral resource depletion from coking, sintering, blast furnace and steel scrap recycling. And climate change, human toxicity, aquatic ecotoxicity, solid waste take up 30%, 95%, 50% and 90% of the total environmental impact, respectively. The major environmental impact of electric furnace steelmaking process includes mainly climate change, acidification and photochemical ozone formation from the molten iron and electric steelmaking processes. So a reliable basis of for decision making for iron and steel enterprises to adjust two different processes is provided. And the research helps to accurately discover energy saving, reduce the potential for environmental load in various aspects of the production process, thus contribute to iron and steel enterprises to improve or optimize production processes.