Since the 21st century, chronic diseases have become a worldwide health problem due to their high morbidity and mortality. Soybean bioactive substances, especially soybean peptides, are considered to have health benefits beyond nutritional effects. As the most studied peptide in soybean, lunasin has been proven to exert beneficial effects on various chronic disorders. This review summarizes the content of lunasin in soybeans, soy derived foods, and other crops, as well as its structural characteristics and bioavailability. Moreover, we focused on the relationship between the physicochemical characteristics and structural composition of lunasin, and its significance for the bioactivities of lunasin. Ultimately, the therapeutic effects of lunasin on cancer, oxidative stress, inflammation, immune response, and hyperlipidemia were described, as well as the molecular mechanisms involved in these impacts. In conclusion, lunasin is a promising multifunctional bioactive peptide, yet further research is required to optimize and expedite its application in the food industry.