Lactic acid bacteria are widely used as probiotics in food fermentation and exhibit various health-promoting properties. This study describes the effects of lactic acid bacteria (LAB) on the phenolic profiles, antioxidant activities, and enzyme inhibition prosperities of blueberry juice. Three different strains (Lactobacillus acidophilus JYLA-16, Lactobacillus plantarum JYLP-375, and Lactobacillus rhamnosus JYLR-005) were selected to ferment the blueberry juice at 37 °C for 48 h. After fermentation, the content of total phenolics and flavonoids increased. Meanwhile, the UPLC-LTQ-MS/MS system conducted the biotransformation of phenols during fermentation. LAB fermentation induced an upgraded trend of syringic acid, ferulic acid, erucic acid, rutin, catechin, epicatechin, and isoorientin. Pearson's correlation analysis revealed that phenolics' metabolism probably contributed to enhancing antioxidant activities. LAB also improved active ingredient retention and antioxidant capacities after in vitro simulated digestion. Finally, we investigated the α-glucosidase inhibitory and α-amylase inhibition of the fermented juice and found that LAB fermentation could improve the inhibition of these enzymes. This study indicated that LAB fermentation could be an efficient strategy for enhancing functional activities in blueberry juice by bio-transforming the phenolics.