Abstract: Measurement of micronuclei in peripheral blood is usually used to detect chromosome damage and mutagenic action of environmental chemicals in toxicology. The cytokinesis-block micronucleus (CBMN) assay is the most widely used method for measuring micronuclei in human lymphocytes,which has been considered as a useful biomarker to detect chromosome damage and gene stability. In this paper,the formation mechanism,endpoint,and the influencing factors of CBMN and the advantage and disadvantage of CBMN assay is reviewed to boost the use of cytokinesis-block micronucleus in protecting workers exposed to environmental chemicals.