Abstract: The principles of index decomposition of carbon emission were studied. Based on accurate data of economic performance and energy consumption in different regions in Beijing, three different methods of index decomposition, namely, carbon intensity reduction method, reference value adjustment method and trend forecasting method were compared. In order to achieve the current goal of carbon emission reduction in Beijing, a methodology of index decomposition of carbon emission based on the reduction of energy and economic index was explored. Based on historical data and estimated value on carbon emission index, the possible carbon intensity reduction rate was calculated which was caused by structural, technical energy conservation as well as energy substitution in the forthcoming period in different regions of Beijing. The results are further tested with the energy development forecasts of different regions and their positioning of regional function, and then the final index decomposition of carbon emission in these regions in the forthcoming period are formed.