Abstract: The composition and content of anthocyanins in bilberry extract and its antioxidant activities in vitro were determined. The anthocyanin composition in the bilberry extract was identified by high performance liquid chromatography coupled with mass spectrometry and the content of anthocyanin was determined with cyanidin-3-O-glucoside as standard. Taking V_C as control,the scavenging ability of bilberry extract to DPPH free radical,ABTS free radical and hydroxyl free radical were determined,and its reducing power and total antioxidant capacity were determined. The results showed that there were fourteen anthocyanins in bilberry extract,which contented delphinidin derivatives,cyanidin derivatives,petunidin derivatives,peonidin derivatives and malvidin derivatives. The total anthocyanins content was 408.74 μg/mg,of which the content of cyanidin was the highest,was 159.93 μg/mg,accounting for 39.12%. The antioxidant activity experiments in vitro showed that the IC₅₀ of DPPH free radical scavenging ability,ABTS free radical scavenging ability and hydroxyl radical scavenging ability of bilberry extract were 26.16,13.07,1.91 mg/mL. The reducing power reached 0.617 when the concentration was 250 μg/mL. This study provides a certain theoretical and data basis for the development and utilization of bilberry.