China in 2009 announced the binding target of its CO2 emissions in 2020: reduce its CO2 emission intensity by 40–45% relative to 2005. In this article, stocks and flows model is used to carry out substance flow analysis toward energy- and limestone-related carbons in China from 1991 to 2007. Then, the possible paths which China can take to achieve this target are presented and discussed in scenario analysis. It is found that (1) conversion into secondary energy, electricity and heat, and limestone calcinations contributed most to the ever-increasing carbon consumption of China during 1991–2007, (2) secondary industry is the biggest carbon consumer and emitter within Chinese economy, and the percentage of carbons emitted by households fell from 1991 to 2007, (3) CO2 emission intensities of three industries and China fell from 1991 to 2002, and then fluctuated during 2002–2007, and (4) both the adjustment in economic structure and the decline in secondary industry’s CO2 emission intensity can influence China’s CO2 emission intensity in an independent way. The emission target can be realized in 2020 when the former becomes 6%:40%:54% and meanwhile the latter decreases to 4.01 tons CO2/10,000 RMB in constant 2000 price. Finally, several policy suggestions are made.