Abstract: Sweet sorghum acts as one of the most promising crops for non-food bioethanol industry in China. In this study, four regions around China, namely East Heilongjiang, Central Xinjiang, North Shandong and Hainan are chosen to calculate the greenhouse gas(GHG) emission of sweet sorghum ethanol production and identify the main factors of the emission. Three scenarios for the sorghum bagasse byproduct re-use are designed for the calculation. The results show that 1) life cycle GHG emission of the four regions in the baseline scenario was 66%-77% that of 90# gasoline with the same heat value; 2) crop planting was a most important secsion affecting the life cycle GHG emission and the utilizations of diesel, electricity and N fertilizer in agricultral production were the main emission factors; 3) the utilization of bagasse byproduct can reduce life cycle GHG emission of sweet sorghum ethanol by 50%-64%. It can provide a reference for establishment of relative policy of sweet sorghum ethanol mass procluctim.