Abstract: As the first cyclin-dependent kinases 4 and 6 inhibitors, palbociclib significantly improved the survival of the patients with the hormone receptor-positive and human epidermal growth factor receptor-2 negative breast cancer. Palbociclib is a crucial landmark in the development history of antineoplastic drugs. This article reviews the mechanism of palbociclib, and summarizes the clinical trials, side effects, and the application of palbociclib.