Abstract This study analyzed the effects of the construction of sponge cities in China, in recent years, on carbon emission reduction based on the global emission reduction targets and China’s responsibility in reducing carbon emissions. Sponge cities are built with rainwater infiltration, retention, storage, purification, reuse, and drainage facilities to promote natural accumulation, natural infiltration, and natural purification of precipitation in urban spaces. In the process, sponge city construction, by intensifying the treatment of urban sewage, increases the urban green area and expands the urban water surface. The increase in urban greening, expansion of wetlands in urban rivers and lakes, and use of rainwater resources lead to carbon reduction effects in the city. Considering the city of Xiamen as an example and combining the main measures for the construction of a sponge city in Xiamen, our quantitative analysis suggested that urban greening can reduce carbon emissions by 66,266.7 tons per year, and the lake and river wetlands can reduce carbon emissions by 962.8 tons per year. The use of rainwater resources in this sponge city can reduce carbon emissions by 2719.1 tons per year. This shows that emission reductions from the construction of China’s sponge cities are significant, resulting in effective responses to and mitigation of climate change.