Abstract: XIAP, c-IAP1 and c-IAP2 are important targets for antitumor drug development. They share the common feature of containing three BIR domains. Many small molecule inhibitors targeting the BIR2 and BIR3 domains of these IAPs have been reported with relatively few BIR2-selective IAPs inhibitors. Unlike BIR3-selective IAPs inhibitors, BIR2-selective IAPs inhibitors can block the interaction of XIAP with Caspase-3 and Caspase-7, so they are a new class of IAPs inhibitors with different mechanisms. The study of these compounds is important to further elucidate the mechanisms of action of IAPs and IAPs inhibitors This paper reviews the structure and function of IAPs, the function of Smac and its interaction with IAPs, and the research progress of BIR2-selective IAPs inhibitors, in order to provide some reference for related research.