Apoptosis inhibitor of macrophage (AIM) belongs to group B of the scavenger receptor cysteine richsuper family. AIM is a soluble protein secreted by macrophages. The expression of this protein is controlled by the liver X receptor. AIM, which is secreted by macrophages, plays important and broad roles in the immune responses of the body. It not only inhibits the apoptosis of macrophages but also participates in the regulation of macrophage polarization. In addition, studies have revealed that AIM is involved in various physiological and pathological processes, such as inflammation, obesity, atherosclerosis, and cancer. It has been used as a biological marker for the diagnosis of diseases such as tuberculosis and liver cirrhosis. Moreover, it can promote the lipolysis of adipose cells by inhibiting the activity of fatty acid synthase ( FAS), playing an important role in the regulation of lipid homeostasis, lipid metabolism, and autoimmune diseases. In this paper, we review the multiple functional characteristics of AIM and its effects on inflammation, lipid metabolism, and related diseases to provide a theoretical basis for relevant medical research.