Abstract: In order to explore the changes of the nutritional value of fermented peanuts and the allergenicity of their proteins to the body,and to apply microbial fermentation to the process of peanut products greatly. In the experiment,peanut pulp(RPP),the research object,was autoclaved(121 ℃,20 min)and fermented by Bacillus natto for 12~60 h in turn. Then physicochemical properties of peanut freeze-dried products were detected,at the same time the change of allergenicity of peanut protein during simulated gastrointestinal digestion was evaluated by SDS-PAGE and ELISA. The results showed that the molecular weight,allergenicity and the soluble protein content of RPP were decreased,and the hydrolysis degree and the polypeptide content were increased when RPP was autoclaved. In addition,when autoclaved RPP was further fermented by Bacillus natto,with the prolongation of fermentation time,protein molecular weight and its allergenicity were decreased furtherly,degree of hydrolysis was further increased,contents of polypeptide and soluble protein were increased first and then decreased. The highest increase rates of degree of hydrolysis,polypeptide and soluble protein content were 106.9%(fermenting for 60 h),339.6%(fermenting for 48 h)and 42.8%(fermenting for 36 h),respectively. In the simulated digestion process,the decrease of peanuts allergenicity mainly occurred in the digestion of gastric juice,the continuous effect of gastric juice and intestinal juice was better than the single effect. Taking all results of the sepreceding physicochemical indexes and allergenicity into consideration,it was concluded that RPP fermented by Bacillus natto for 36 h was the best among all fermented peanut products,having higher nutritional value,great physicochemical properties and lower allergenicity. And its allergenicity was kept at a low level in the process of gastrointestinal digestion.