Vaccines are among the most effective measures for preventing infectious diseases and play a crucial role in controlling the spread of these diseases. Adjuvants, serving as auxiliary components in vaccines, are indispensable in the vaccine development process. Ideal adjuvants not only enhance the immune response, enabling the body to achieve optimal protective immunity but also play important roles in reducing the dosage of immunogens and lowering vaccine production costs. To meet the demands of novel vaccines, many new types of adjuvants have been developed. However, there is still a lack of adjuvants that are safe, effective, easy to prepare, highly pure, and suitable for a variety of vaccines in clinical settings. This article categorizes adjuvants and summarizes their mechanisms of action and characteristics, focusing on traditional aluminum salt adjuvants and more modern lipid-based and nucleic acid-based adjuvants. The summary is based on a computer search of databases including PubMed, Embase, The Cochrane Library, CNKI (China National Knowledge Infrastructure), VIP Database, and Wanfang Database, using English search keywords such as Adjuvants, Vaccine, Vaccine Adjuvant, aluminum salts, MF59, AS03, Toll-like receptor agonist, etc., and corresponding Chinese search terms. The aim is to provide references for the development and application of adjuvants.