Alliumis a common functional vegetable with edible and medicinal value.Alliumplants have a special spicy taste, so they are often used as food and seasoning in people’s diets. As a functional food,Alliumalso has abundant biological activities, some of which are used as drugs to treat diseases. By consumingAlliumon a daily basis, people can receive active compounds of natural origin, thereby improving their health status and reducing the likelihood of disease. Steroidal saponins are important secondary metabolites ofAllium, which are formed by the steroidal aglycone group and sugar. Steroidal saponins have various physiological activities, such as hypoglycemic, antiplatelet aggregation, anti-inflammatory, antitumor, antimicrobial, and enzyme activity inhibition, which is one of the key reasons whyAlliumhas such significant health benefits. The structural diversity and rich biological activities of steroidal saponins makeAlliumimportant plants for both food and medicine. In this paper, the chemical structures, biological activities, and structure–activity relationships of steroidal saponins isolated fromAlliumare reviewed, and the biosynthetic pathways of some key compounds are proposed as well, to provide a molecular reference basis based on secondary metabolites for the health value ofAllium.