Abstract: In order to investigate the fermentation characteristics of blueberry juice fermented by lactic acid bacteria, fresh blueberry was used as raw materials, and the fermented blueberry juice was prepared by lactic acid bacteria fermentation. On the basis of single factor experiment, the optimal preparation conditions of blueberry juice fermented by lactic acid bacteria were obtained using the Box-Behnken center combination test and response surface analysis method with SOD enzyme activity as an indicator. The total phenols, anthocyanins, total sugars, viable bacteria and antioxidant activity of blueberry juice before and after fermentation were determined. The results showed that the optimal technological conditions for preparing fermented blueberry juice were:the fermentation time was 24 h, the fermentation temperature was 37℃, the inoculation amount of lactic acid bacteria was 0.1%, and the addition amount of sucrose was 6%. Under the optimum conditions, The SOD enzyme activity of fermented blueberry juice was 261.63 U/mL, which was close to the theoretical value. The number of viable lactic acid bacteria was 2.18×10¹¹CFU/mL. The fermentation temperature and initial inoculation amount had a significant effect on antioxidant enzyme activity, and the interaction between inoculation amount and time was very significant, the interaction of other factors was not significant. Compared with that before fermentation, the content of total phenols and total anthocyanins in fermented blueberry juice increased, which was 413.40 mg/L and 206.40 mg/L respectively. The antioxidant activity of fermented blueberry juice was improved. The scavenging rate of ABTS⁺ and ·OH radical by fermented blueberry juice increased significantly, and the scavenging rate of DPPH radical reached 99. 4%. The anthocyanin monomer in the fermentation of blueberry juice was detected by HPLC. The results showed that the species of anthocyanin monomer components did not change, but the content changed significantly. Among them, the content of anthocyanin components of 6 monomers increased first and then decreased with the extension of fermentation time, the content of anthocyanin components of 4 monomers decreased with the extension of fermentation time, and the content of anthocyanin components of 3 monomers increased significantly with the extension of fermentation time. The main anthocyanin monomer in blueberry juice was malvidin-3-O-galactoside, and the content was 59.59 μg/mL after fermentation for 24h. The content of the other two main components, malvidin-3-O-glucoside (t_R=31.006 min) and cyanidin-3-O-galactoside (t_R=23.394 min), decreased significantly with the extension of fermentation time. The results can provide a theoretical basis for the comprehensive utilization of blueberry resources.