Two major approaches exist for mitigating CO2 emission in east China (including Jiangsu province, Zhejiang province. and Shanghai City, also called JZS district). One is to raise the efficiency of energy use and conserve energy. The other is to gradually change the structure of the energy system, that is, to advocate the use of alternative energy, such as hydropower, solar energy, wind energy, and biomass. and in the meantime decrease the use of fossil fuels. The latter approach will be studied in this paper for the JZS district. The use of renewable energy is very small, less than 0.5% of the total energy supply in 1990 (except for the now available hydraulic power generation, which accounts for 5.5% of the total energy supply today). It is estimated that the use of renewable energy will reach 5.78 Mtce, 2.8% of the total energy supply in 2000. The use of renewable energy will reduce CO2 emissions by 15.3 Mt, 5.6% of the emission level in 1990. By 2010, the use of renewable energy will reach 18.75 Mtce, reducing CO2 emission by 49.65 Mt, 18.1% of the emissions in 1990.