Abstract: As a part of novel drug delivery carriers, peptides have diverse biological activities, low immunogenicity and good biocompatibility. In recent years, studies on the delivery carriers modified by peptides have attracted much attention. Among them, the peptides with acid sensitivity can change their secondary structures under slightly acidic microenvironment of the tumor or in lysosome. Therefore, the carriers made or modified by acid-sensitive peptides can specifically release the loaded drug in the tumor tissue, enhance the cell internalization of drugs and improve its therapeutic effects. In accordance with acid-sensitive peptides studied, the side chains, number of polar residues, sequence and secondary structure of the peptides might be involved in the acid sensitivity. In this review, we summarize the acid-sensitive peptides from recent literatures, analyze the connection between the structure and the acid sensitivity, and focus on the mechanism and application of acid-sensitive peptides in drug delivery. This provides the basis for further development and utilization for acid-sensitive peptides for efficient drug delivery.