This paper reports the cytokinesis-block micronucleus method in micro-blood cultures. It was performed that CB method in comparison with conventional micronucleus (CM) method for detection induced micronuciei of different doses of ,60,Coγ-rays irradation and spontaneous micronucleus of different ages. The results showed that direct peripheral micro-blood cultures also obtained the cytoknesisblock micronuclei. Using CB method, the micronuclei fequency of different ages was a linear relationship, Y=1.62+0.74 D, the spontaneous micronuclei frequency of different ages was 4.14% the induced micronuclei also showed that was a linear relationship, Y=6.01+0.692 D. Using CM method, it showed that the induced micronuclei was a linear relationship, Y=0.486 D-1.968,but there is no significant difference seen between the micronuclei frequency of different ages. Comparison with CM and direct blood smear methods confirmed that the cytokinesis-block method of micro-blood cultures is more sensitive and precise.