The ultrasonic-assisted ethanol-ammonium sulfate aqueous two-phase system was adopted to extract polyphenols from finger millet. The extraction process was optimized by single factor test and response surface analysis, polyphenols yield as the index. The results showed that the optimum extraction process was determined as follows: ethanol volume fraction of 41%, ammonium sulfate concentration of 0.3 g/mL, ultrasonic temperature of 42 ℃, liquid-solid ratio of 60 mL/g, and treated for 29 min. By adopting the process, the extraction yield of polyphenols was 319.15 mg/100 g. Finger millet polyphenols had strong antioxidant activity in vitro, the total reducing capacity, DPPH radical scavenging activity, hydroxyl radical scavenging ability reached 91.84%, 96.79% and 89.03% of V_C at the same concentration, respectively.