Abstract: Blueberry Jiaosu fermented by using wild blueberries (Vaccinium uliginosum L) was used as raw materials. The changes of the total anthocyanin, phenolic, flavonoid contents, and antioxidant capacity in vitro during fermentation were detected. Caenorhabditis elegans were used to determine the antioxidant activity in vivo, preliminarily explored the related mechanism of antioxidant of blueberry Jiaosu. The results showed that the total anthocyanin content increased firstly and then decreased, reaching 0.52 mg/mL on the 50th day. The total phenolic and flavonoid contents kept increasing and reached their maximum level (2.81 mg/mL, 3.17 mg/mL, respectively) on the 300th day. In C.elegans, the results showed that blueberry Jiaosu could prolong the lifespan of C.elegans, enhance its oxidative stress ability under the stimulation of hydrogen peroxide, increase the activities of superoxide dismutase, catalase and glutathione peroxidase, and reduce the content of reactive oxygen species and malondialdehyde. These indicate that blueberry Jiaosu may increase the activity of antioxidant enzymes to reduce the oxidative damage of Caenorhabditis elegans.