Abstract: The carbon emission factor of steel is a critical basis for carbon emission accounting in civil and structural engineering. Nevertheless， the existing factors provided by current standards and literature exhibit significant variability and fail to reflect the time-varying characteristic of steel industry evolution. This paper collected production inventory data from 10 representative Chinese iron & steel enterprises using blast furnaces and converters as their main production equipment， along with data provided by the statistical annual reports from the China Iron & Steel Association. Based upon this， a material and energy inventory database was established for structural steel products over the past five years. By using the input-output method， the carbon emission factors for steel products were calculated from these statistical data. Considering the environmental performance data provided by the steel industry Environmental Product Declaration （EPD） platform， the data samples and statistical parameters for the carbon emission factors of steel rebars， section steel， steel plates， and general steel products were established. Based on this analysis， recommended values for the carbon emission factors of commonly-used steel products in civil and structural engineering were proposed. The main conclusions are as follows： 1） The recommended carbon emission factors for steel rebars， section steels， and steel plates are 2150 kg CO₂e/t， 2260 kg CO₂e/t， and 2240 kg CO₂e/t， respectively. 2） The carbon emission factors of steel rebars， section steel， and steel plates calculated herein are 190 kg CO₂e/t， 105 kg CO₂e/t， and 160 kg CO₂e/t lower，respectively， than the corresponding values specified in the Standard for Building Carbon Emission Calculation（GB/T 51366-2019）， demonstrating evident decarbonization of these steel products over the past five years. 3） Compared to the carbon emission factors reported in the 2004 literature， the values calculated in this study show a reduction of more than 1300 kg CO₂e/t for steel rebars， section steel， and steel plates， demonstrating the remarkable progress in the green and low-carbon development of structural steel products in China over the past two decades.