Abstract: Extracellular signal-regulated kinase (ERK) is a kind of serine/threonine protein kinase. As a key downstream protein in RAS-RAF-MEK-ERK signaling pathway, its abnormal activation plays an important role in the development of tumors. Selective ERK1/2 inhibitors can block ERK signaling pathway while overcoming drug resistance caused by upstream target mutation. In this paper, the components of MAPK signaling pathway, the structure and functions of ERK and the role of ERK signaling pathway in tumor development are summarized, and some representative ERK inhibitors in clinical or preclinical studies are emphasized.