Soyasaponins are abundantly present in soybean germ, hypocotyl, and other parts, especially in defatted soybean meal, which can be produced as a high-value-added product to improve the utilization of by-products in soybean oil processing. Soyasaponins belong to pentacyclic triterpenoid compounds and are a type of dammarane-type saponin composed of hydrophobic aglycone and hydrophilic sugar group. They possess certain amphiphilic properties and various physiological activities, including anti-tumor, anti-inflammatory, antioxidant, immune-modulating, and hepatoprotective effects. In recent years, the research areas of soyasaponins have been continuously expanded from activity verification to molecular mechanisms, producing a number of forward-looking achievements. Soyasaponins with different structures and types exhibit different physiological activities and mechanisms of action, and related research provided a theoretical basis for the application of soyasaponins in food and medicine. This article focused on the latest research progress on the structure and classification, physiological activities, and structure-activity relationships of soyasaponins, analyzed the influence of processing methods on the structure of soyasaponins, summarized the mechanisms of soyasaponins in exerting physiological activities and their applications based on physiological activities, and illustrated the problems that need to be addressed in the future application of soyasaponins, aiming to provide a theoretical basis for further research and development of soyasaponins.