To investigate ultrasonic method of total saponins from S.tetradonta and study the antioxidant activities. By using the single factor experiment and response surface methodology, taking he total saponin yields as the response value, the extraction procees was optimized. Meanwhile, UV spectrophotometry were used to determine the abilities of total saponins from S.tetradonta on scavenging DPPH·, ABTS· and FRAP assay. The results indicated that the optimal extraction conditions were as follows: ultrasonic time 40 min, ratio of water to material 30 mL/g, and ethanol concentration 77%. Under these conditions, the content of total saponins reached 3.1 mg/g. The total saponins from S.tetradonta had a strong ability to scavenge of DPPH·. And its total reducing power assays and ABTS· scavenging effect were relatively weak.