Abstract: Steam explosion as an effective pretreatment can separate hemi-cellulose, cellulose and lignin from lignocelluloses such as stalk and wood, and enhance yield of production from lignocelluloses with chemical and biological methods. Energy balance of corn stalk steam explosion and anaerobic fermentation were analyzed based on the experiments in the paper. The energy conversion rate of anaerobic fermentation with steam exploded corn stalk increased with the increasing of steam pressure at the same pressure retention time, and the maximums in the same steam pressure were got at the 90 s pressure retention time in each group. The minimum and maximum energy conversion rates of anaerobic fermentation with steam exploded corn stalk were 8.39% and 11.68% at room temperature, which are 1.38 times and 1.92 times than that of the control. But the analysis of incremental benefit-cost ratio showed the expended energy for steam explosion is greater than the increased additional energy output in anaerobic fermentation with steam exploded corn stalk compared with the control. From this point of view, it is not an economic way for steam explosion method.