Abstract: In this study,ultrasound-assisted extraction of total flavonoids from Chishui white tea was optimized using response surface methodology(RSM),and their antioxidant activities were investigated. RSM was used to optimize the ultrasound-assisted extraction parameters for total flavonoids based on the single-factor test results. A Box-Behnken design(BBD)with three factors(methanol concentration,liquid-solid ratio and extraction time)was performed. The extraction yield of total flavonoids was taken as the response. The results showed that the optimized conditions for achieving the maximum yield of total flavonoids were 69% methanol concentration,24 min extraction time and 102:1 mL/g liquid-solid ratio. Under these conditions,obtained yield value(243.50 mg RE/g)was in total agreement with value predicted by the model executed by BBD(241.14 mg RE/g). In vitro assays showed that the total flavonoids of Chishui white tea had strong free radical scavenging capacity and certain reducing power. The scavenging activities of DPPH free radicals,ATBS free radicals and the ferrous ions were up to 90.1%,99.8% and 81.33%,respectively,and the corresponding half maximal inhibitory concentration(IC₅₀)were 0.082,0.027 and 0.781 mg/mL,respectively. Thus,it is stable and reliable to optimize the extraction method of total flavonoids from Chishui white tea. Furthermore,the total flavonoids obtained under optimum extraction conditions exhibited strong antioxidant activities,indicating that the flavonoids from Chishui white tea could be used as a potential source of natural antioxidants.