Polo-like kinase 1(PLK1) is a highly conserved serine/threonine protein kinases that plays a key role in regulation of mitosis.In about 80% of human tumors,of various origins,PLK1 is over expressed.Over-expression of PLK1 is associated with a poor prognosis in several tumor types and a lower overall survival rate.PLK1 inhibitor can interfere with different stages of mitosis,such as centrosome maturation,spindle formation,chromosome separation,and cytokinesis.This review includes an overview of PLK1 inhibitor in clinical and preclinical development.