Lignocellulosic biomass could play a greatly expanded role as a source of alcohol fermentation.Mechanism that control xylan release with decreasing of DP during mechanical grinding of lignocellulosic biomass were explored by FTIR, UV and GC.The explanation for these phenomena was that lignin was removed and lignin-xylan compounds play an important role in the hydrolysis of lignocellulosic biomass.The results showed that the lower DP of lignocellulosic biomass, the more severe was the damage to cellulose high-level structure.Ether, glycosidic, and acetal bonds, as well as some other lignin-xylan complexes chemical binding were affected.When the DP is very low, one can expect a lot of xylose dissolution.Therefore,for alcohol fermentation it is important to first select or modify the DP of cellulose in the biomass.The results showed that the decreasing of DP from 521 to 77 affected the contents of glucose, which increased from 5.31 g/L to 31.1g/L, and 5.72g/L xylose were released from lignocellulosic biomass.