Abstract: Blueberry juice was fermented by Lactobacillus plantarum LJ26,and the fermentation process was optimized by Box-Benhnken design response test. The optimized fermentation conditions were as follows:initial inoculum size was 3%,fermentation temperature was 37℃ and fermentation time 24 h. Under the optimum conditions,the viable counts of fermented blueberry juice were 1×10⁹ cfu/mL. In addition,the functional substances in the blueberry juice were compared before and after the fermentation. The results showed that phenolic content and the anthocyanin content were increased by 43.42% and 5.88%,respectively. The antioxidant capacities of blueberry juice before and after fermentation were detected by in vitro free radical scavenging test and Caco-2 cell oxidative damage amelioration test. It was found that the free radical scavenging rate of DPPH and the superoxide anion of blueberry juice increased significantly and the alleviation ability of Caco-2 cell oxidative damage was also significantly elevated after fermentation. These results proved that L. plantarum LJ26 could enhance the quality of blueberry juice,and provided a theoretical basis for the deep processing technology of blueberry.