A promising option for long-term storage of CO2 is to fix CO2 by industrial solid wastes, such as basic oxygen furnace (BOF) steelmaking slag. It is advantage to use BOF steelmaking slag to fix CO2, such as large volume of BOF steelmaking slag, low price of raw materials, close to the CO2 emission sources, and no secondary pollution. It is of great significance to the CO2 emissions reduction and solid waste disposal in the ironmaking and steelmaking plant. In this paper, the leaching process, impurities removing and carbonation of steelmaking plant waste slag were studied at ambient pressure. The results show that Ca2+ leaching mainly occurs at the beginning 60min in the leaching process. The Ca2+ leaching ratio can reach about 45% with the leachant of 2mol/L HAc, leaching temperature of 30°C and solid-liquid ratio of 1:20. Moreover, it can effectively remove Mg2+, Al3+ and Fe3+ by adding small amounts of NaOH and triethanolamine in the leaching solution, and thereafter, high purity CaCO3 products can be obtained through the carbonation process.