Diabetes mellitus (DM) is a metabolic disease, and diabetes patients have long-term higher blood sugar levels than standard. Most people with diabetes have complications that greatly affect their standard of living. Patients with type 2 DM occupy the vast majority of all diabetes patients. Glucagonlike peptide-1 (GLP-1) secreted by intestinal enteroendocrine L-cells is a small molecule polypeptide, which is glucose concentration-dependent and can effectively reduce blood glucose concentration. Dipeptidyl peptidase-4 (DPP-4) is an important target for the treatment of type 2 DM because it can degrade GLP-1. DPP-4 inhibitors can enhance the blood glucose lowering effect of GLP-1 by inhibiting DPP-4. This article summarizes the development of DPP-4 inhibitors from 2015 to 2019, and can provide helpful information for the discovery of novel DPP-4 inhibitors in the future.