In this paper,quinoa saponins as the research object,based on single factor experiment,with saponins extraction yield as index,through response surface method optimization,combined with quinoa powder SEM characterization,in order to obtain the optimal process parameters of ultrasonic-vacuum extraction of saponins.After the crude extract of quinoa saponins was extracted with n-butanol,its antioxidant activity and related mechanism were investigated.The experimental results showed that the optimal process parameters for the extraction of quinoa saponins by ultrasonic-negative pressure method were as follows∶ultrasonic time 20 min,ultrasonic temperature 59 ℃,negative pressure 0.064 MPa.Under this condition,extraction yield was the highest (the predicting value was 12.37 mg/g,and the experimental value was 11.95±0.034 mg/g).The influence order of the three factors on the yield of quinoa saponins was as follows∶negative pressure > ultrasonic temperature > ultrasonic time.Quinoa saponins had strong reducing power and DPPH free radical scavenging ability in the concentration range (0-0.25 mg/mL),and its antioxidant activity was positively correlated with its concentration.