In order to quantify the carbon emissions during the construction and operation of sponge cities and analyze the key influencing factors of carbon emissions, a 100km² area in Beijing was taken as the study area, estimates of carbon emissions from the construction and operation of its sponge city, the relationship between carbon emission and control indexes such as proportion of qualified area, control rate of total runoff and proportion of pressure flow pipe network in sponge city was analyzed. The results show that the carbon emission of sponge city is mainly concentrated in the material production stage, and the hidden carbon in the material of most facilities accounts for more than 80% of the total carbon emission in the construction stage, and the construction-related carbon emission is relatively small. Under the same stormwater control level, the carbon emission of grey stormwater infrastructure is higher than that of green stormwater infrastructure; During the 30-year life cycle of the study area, the carbon emissions during construction and operation stages (in terms of CO₂) were 173 600t and -167100t, respectively. The key factors affecting carbon emission in the construction and operation of sponge cities are the proportion of qualified area, annual total runoff control rate and drainage mode, for every 1% increase in the proportion of the area up to the standard and in the control rate of annual total runoff, the carbon emissions in the whole life of the sponge city will be reduced by 1900t and 2500t respectively, and the proportion of the pressure flow pipe network will be reduced by 1% , carbon emissions during the whole life cycle were reduced by 249t on average.