We decompose factors affecting Jiangsu's CO2 emissions at holistic sectoral and sub-sectoral levels. The transfers-out and investment effects greatly increased Jiangsu's CO2 emissions. Jiangsu's foreign trade increased CO2 emissions and its structure was in a deteriorating state. The energy intensity had a great reducing effect on CO2 emissions but energy structure had a slight effect. Effects of composition factors on CO2 emissions in sectors and subsectors differed greatly.