Objective As an important mode of transport connecting urban agglomerations and metropolitan areas, the construction scale of suburban railways has been expanding rapidly in recent years. However, the consumption of construction materials, energy usage, and construction organization at the construction stage of city railways results in relatively high carbon emission intensity. Therefore, it is necessary to systematically examine the carbon emission characteristics and key emission sources at suburban railway construction stage, explore low-carbon optimization pathways, and provide scientific support for the green and low-carbon transformation of the industry as well as the implementation of national 'dual-carbon' strategy.

Method Based on ISO 14064 and relevant domestic and international standards including the Standard for Building Carbon Emission Calculation, The time boundary, spatial boundary and engineering scope boundary of the urban rail civil construction stage are delimited, and the temporal and spatial boundaries of suburban railway construction stage are defined, and a carbon emission calculation model is established using carbon emission factor method. Taking a city railway line as an example, and incorporating bill-of-quantities data, the carbon emission characteristics of stations （underground and elevated） and line sections （underground and above-ground） are quantitatively analyzed, and differences in carbon emissions across different stages are comparatively examined.

Result & Conclusion  The building material production stage is the primary source of carbon emissions, accounting for more than 70% of total emissions, with concrete and reinforcing steel contributing over 80%. For projects of the same scale, carbon emissions from underground stations are 35% higher than those from above-ground sections. The unit-length carbon emission intensity during the construction stage of line sections is higher than that of station projects.