Abstract: Response surface method was used to optimize the extraction technology of total flavonoids from Cuscuta chinesis. On the basis of single-factor test,ethanol concentration,extraction temperature and ratio of water to materials and extraction time were optimized by the Box-Behnken design and response surface method,and the yield of total flavonoids was used as the responsive values. Meanwhile,the antioxidant capacity was measured by scavenging of DPPH·,hydroxyl free radical and superoxide free radical. The results showed that the optimum extraction conditions were as follows:Ethanol concentration was 90%,extraction temperature was 70 ℃,ratio of raw material to liquid was 1:15 g/mL and extracted for 100 min. Under the conditions,the yield of total flavonoids was(34.65±0.002) mg/g,which had a relative error was 0.81% with the expected yield of 34.37 mg/g. This indicated the refluxing extraction process of total flavonoids from Cuscuta chinesis was stable and reliable. IC₅₀ of total flavonoids from Cuscuta chinesis to DPPH free radical,hydroxyl radical and uperoxide free radical were 0.067,7.209 and 0.119 mg/mL,respectively. IC₅₀ of ascorbic acid to DPPH free radical and hydroxyl radical and uperoxide free radical were 0.082,1.731 and 0.054 mg/mL,respectively. The antioxidant activity in vitro showed that total flavonoids from Cuscuta chinesis had a better scavenging effect on DPPH radical and the DPPH scavenging ability of was obviously higher than that of ascorbic acid. The scavenging ability of hydroxyl radical and superoxide free radical was lower than that of ascorbic acid.