This study was conducted as a part of database construction for development of CO2 assessment system for concrete to assess CO2 emissions and analyze characteristics of blast furnace slag manufactured in Korea through life cycle assessment method. For this, life cycle CO2 emissions assessment technique for construction materials was examined. The entire manufacturing process for blast furnace slag was analyzed on blast furnace slag manufacturer in Korea for application of assessment technique. Life cycle CO2 assessment was performed on blast furnace slag after classifying assessment process into raw material production step, raw material transportation step and construction material manufacture step.