Objective To investigate the composition and antioxidant properties of flavonoids from the Ampelopsis grossedentata leaf extract.Methods Qualitative identification and quantitative determination are conducted on flavonoids from the extract by high-performance liquid chromatography (HPLC). Then, with tea polyphenols and vitamin C as controls, the scavenging rates of the extract are determined against four free radicals, including OH^-, DPPH, O2-, and ABTS⁺, and the antioxidant effect of the extract is studied during potato chip storage.Results The results show that the flavonoid and polyphenol content of the extract are 41.07% and 45.50%, respectively. There are five types of flavonoids in the extract, namely dihydromyricetin, taxifolin, vitexin, rutin, and quercetin. Among the flavonoids mentioned, dihydromyricetin is the primary one in A. grossedentata. Compared to tea polyphenols and vitamin C, the extract at the same concentration exhibits higher OH^-, DPPH, O2-, and ABTS⁺ free radical scavenging rate, indicating a stronger in vitro antioxidant capacity than the control. The antioxidant capacity of the extract under acidic conditions is stronger than that under neutral and alkaline conditions. During the 8-month storage period, the extract demonstrates significant antioxidant effects on potato chips (P<0.05).Conclusion The antioxidant active ingredient content in A. grossedentata extract is as high as 86%, indicating a strong antioxidant capacity. Therefore, the extract can be developed as a food antioxidant and raw material for functional food.