The invention relates to a method for producing high density ethanol without enzyme addition by taking inulin biomass as a raw material, according to the invention, saccharomyces cerevisiae DQ1 is taken as fermentation strain, inulase production, monosaccharide generation by catalyzing inulin through inulase, ethanol production by fermenting through monosaccharide can be carried out in one bioreactor for realizing highly integration of the process; a novel threaded belt paddle reactor capable of treating high solid content is used, and enzyme production, saccharification and high density ethanol fermentation can be carried out under the condition of high solid content inulin biomass raw material. The method has the following advantages that saccharomyces cerevisiae is provided for directly fermenting the inulin biomass to produce ethanol, so that the integration of the processes of enzyme production, saccharification and ethanol fermentation enables synchronous realization, exogenous inulase addition can be avoided, the production cost of ethanol can be reduced; the novel threaded belt paddle reactor can treat substrate series with high solid content and high viscosity, thereby ethanol concentration in a broth is increased, and the distillation energy consumption and production cost of ethanol can be reduced.