Carbon emission from sewage treatment in the period from 2000 to 2009 in Chongqing was esti-mated based on the methods recommended by IPCC (Intergovernmental Panel on Climate Change) and a-dopted in China. Total carbon emission consisted of direct emission, i.e. emission of CH_4 and N_2O resul-ting directly from biochemical reaction in sewage treatment, and indirect emission, i.e. emission of CO_2 resulting from power consumption. The results showed that the cumulative carbon emission from wastewater treatment was 205.24 million tons (CO_2-eq) from 2000 to 2009 in Chongqing. Carbon emission from domestic sewage treatment grew yearly, with an annual average increase of 50%. The emission of CH_4, N_2O and CO_2 accounted for 45.25%, 28.62% and 26.13%, respectively, of the total. Carbon emis-sion per capita increased with an annual rate of 46.68%. Carbon emission levels intensity decreased contin-uously, the annual decrease rate being 32.4%.