Abstract: The mesophilic and thermophilic anaerobic digestion（AD）of rape straw with biochar and ethanol addition were studied. The effects of ethanol addition on the biogas yield,degradation of lignocellulose and bacterial community were explored. The results showed that biochar and ethanol addition improved the biogas yield and degradation of cellulose. The biogas yield increased first and then decreased with the increase of the ethanol dosage. When the ethanol dosage was 3 g/L,the biogas yields in mesophilic and thermophilic AD were the highest,219.3 mL/g and 240.5 mL/g,respectively. For the lignocellulose degradation,the cellulose content in mesophilic AD with 3 g/L ethanol was reduced from 54.00% of the pretreated straw to 18.69%-25.03%.Microbial community results showed that the relative abundances of Firmicutes and Bacteroides were high in the biogas residue of mesophilic AD with 3 g/L ethanol. This revealed the mechanism of biochar and ethanol addition to promote biogas production of rape straw in AD.