This study aimed to determine the optimal CO 2 reduction path for Jiangsu province to achieve the target of 40–45% reduction of CO 2 emissions intensity by 2020 based on the 2005 level. Using the IPAT model combined with scenario analysis, we consider four parameters: economic growth, population growth, energy intensity and renewable-energy share. Each parameter is measured from different scenarios, and 54 kinds of scheme are set to forecast the CO 2 emissions. The forecast results show that it is likely for Jiangsu province to achieve the target. Rapid economic growth is the main determinant that causes increase in CO 2 emissions. Energy-intensity reduction and renewable-energy-share increase have beneficial influences on reducing CO 2 emissions. The effect of energy-share increase is larger than that of energy-intensity reduction. As for the reduction of CO 2 emissions intensity, energy-intensity reduction has a larger influence than renewable-energy-share increase. The optimal development mode until the year 2020 is as follows: the economy and population grow at appropriate rates, energy intensity reaches the level in developed countries, and the renewable-energy share increases to 15% in 2020.