This paper estimates the Marginal Abatement Cost Curve (MACC) of CO2 emissions in China based on a provincial panel for the period of 2001-2010. The provincial marginal abatement cost (MAC) of CO2 emissions is estimated using a parameterized directional output distance function. Four types of model specifications are applied to fit the MAC-carbon intensity pairs. The optimal specification controlling for various covariates is identified econometrically. A scenario simulation of China’s 40-45 percent carbon intensity reduction based on our MACC is illustrated. Our simulation results show that China would incur a 51-57 percent marginal abatement cost increase to achieve a corresponding 40-45 percent reduction in carbon intensity compared to its 2005 level.