Taking the black bean as the main raw material, the total polyphenol content and DPPH radical scavenging rate as the indexes, the single factor experiment and orthogonal experiment design were used to optimize the pre-fermentation conditions of black bean douchi made by bacillus subtilis natto. The results showed that the optimum fermentation conditions were as follows: fermentation time was 4 d, fermentation temperature was 39 ℃, inoculation amount of bacillus subtilis natto was 2.5 g/100 g·black bean. Under this condition the total polyphenol content of black bean douchi was 4.24 mg/g, and the DPPH radical scavenging rate was 79.86%, which indicated that black bean douchi fermented by bacillus subtilis natto could obtain high antioxidant activity.