The extraction process of total steroidal saponins was optimized by the response surface method and its in vitro radical scavenging activity was also evaluated by the methods of α-deoxyribose, pyrogallol autoxidation, DPPH and ABTS. The results showed that the content of total steroidal saponins would be the highest if the time, liquid-solid ratio and temperature of ultrasonic treatment was 0.5 h, 19.51.0 (mL/g) and 39.7 ℃, and the soxhlet extraction time was 3 h. At this point, the Liriopesides B could reach 0.073 8 mg/mL. In addition, the antioxidant activity test showed that steroidal saponins had some antioxidant activities, and positive correlations were found between its antioxidant activities and its concentration. In particular, it had the obvious scavenging activity to OH free radicals and superoxide anions, which reached 59.66% and 52.3% respectively at the highest concentration of 1.28 mg/mL.