In order to standardize the production of traditional douchi, dominant strain QY2b screened from traditional fermented douchi of Qingyang, Gansu and Bacillus subtilis, Rhizopus oryzae and Aspergillus oryzae preserved by CICC was selected as strain. Through four factors and three levels quadratic regression orthogonal rotated combination design and single factor experiment and orthogonal experiment, proportion of mixed strain and fermentation technology were optimized. Also, physiochemical indexes of final product and compounds and relative content of volatile flavor was tested. Results show that under the condition that QY2b: Bacillus subtilis: Rhizopus oryzae: Aspergillus oryzae=1:0.8: 2: 1.3, overall inoculation 1.5%, fermentation temperature 37℃, fermentation time 72h, the dosage of salt 15% and after fermentation 20d, compared with QY2b pure breed fermented douchi, reducing sugar and amino acid nitrogen of mixed strains raised by 22.18% and 82.61% respectively. What is more, total detectable amount of volatile components of douchi increased by 1.76%, chemical compounds raised by four categories of 21 species. All above indicates that mixed strains were superior to QY2b pure breed fermented douchi.