Abstract: The ultrasonic assisted PEG/(NH₄)₂SO₄ aqueous two-phase extraction of total flavonoids from the flowers of Camellia chrysantha and its antioxidant activity were studied. Taking the extraction rate of flavonoids as the index, the extraction process was optimized by orthogonal design on the basis of single factor tests. The antioxidant effect was evaluated by the determination of DPPH· and OH· scavenging rates. Flavonoid compounds including rutin, quercetin and kaempferol in Camellia chrysantha were confirmed by HPLC analysis. The results showed that under the optimum extraction conditions (PEG molecular weight 600, PEG mass fraction 19%, ammonium sulfate mass fraction 20%, ethanol concentration 80%, ultrasonic time 30 min), the extraction rate of flavonoids could reach 98.50%, and the yield of flavonoids could reach 13.54%. The results of antioxidant experiments showed that the IC₅₀ of the flavonoid extract from the flowers of Camellia chrysantha to DPPH· and OH· were 0.070 and 0.679 mg/mL, respectively. The results suggest that the technology of ultrasonic assisted aqueous two-phase extraction of total flavonoids from the flowers of Camellia chrysantha is reasonable, the obtained flavonoids exhibiting good antioxidant capacity and can be further developed and utilized.