Abstract: Setting up the technology of taking the atmospheric pressure drum wind drying method prepare the direct investment type Bacillus natto starter culture. Through optimizing preparation conditions of the direct investment type Bacillus natto starter culture to obtain the optimum preparation technology and measure its fermentation performance and storage stability. The results indicated that the optimum preparation technology of the direct investment type Bacillus natto starter culture was:The compound dry protective agents were 11.07% skim milk powder,6.41% sodium glutamate and 14.76% sodium citrate,the mixing conditions of bacterial sludge and protective agent:the mixing ration of bacterial sludge and protective agent(g/mL)was 1:7,the pH value of compound protective agent was 6.0 and the balance time of bacterial sludge and protective agent was 35 min.The carrier substrate of Bacillus natto was rice flour,and the optimum mixing ration(mL/g)of bacterial suspension and rice flour was 1:2,the drying condition of starter culture was at 50℃ for 9 hours. Under these conditions the survival rate of Bacillus natto reached 82.66%,the bacterial content of prepared starter culture was 7.93×10¹⁰ cfu/g. The fermentation performance and storage stability of the Bacillus natto starter culture were satisfactory,the viable bacterial number and fermentation activity after it stored at 4℃ or -20℃ for 180 d had no obvious change.Therefore,the direct investment type Bacillus natto starter culture which took the atmospheric pressure drum wind drying method was complied with the standard requirements of marketing Bacillus natto starter culture,it can be extended to industrial production,simplify the production processes.