Viscosity is one key bottleneck of high gravity fermentation.The viscosity profiles of both conventional process and no-cook process are investigated using whole ground corn as the raw material.At very high dry solid concentration,it is found that during conventional hot cooking process,the gelatinization and liquefaction become very hard to handle while there is no viscosity issue for no cook process.In addition,the no cook process generate more ethanol than that from conventional process during high gravity fermentation;with the help of raw starch hydrolyzing enzymes,together with commercial dry yeast and temperature staging strategy,ethanol concentration was able to reach up to 20%(v/v) within 98h.