Researches on the structure and distribution and content of soyasaponin were reviewed in detail. The series of soyasaponin include group A, group B, and DDMP saponins. The DDMP-saponin is the genuine saponin existing in soybean seed. Due to unstability, it can be easily decmposed to usual group B or group E saponin. Recent advances on the physiological functions of soyasaponin were reviewed, including anti-cancer activity, anti-HIV activity, and antioxidant activity of DDMP saponin.