In order to study the effect-dosage relationship between the PCC induced by Okadaic acid and the IR dosages, human peripheral blood in vitro was irradiated by X-rays at different doses (0、0.5、1.0、2.0、3.0、5.0Gy) cultivated for 48 hours and added with Okadaic acid two hours before the end of culture. Chromosome aberrations frequencies was analyzed and compared with that induced by the conventional chromosome assay and their dose-response curves were fitted. The results show that the mitotic index of the PCC induced by Okadaic acid is higher than that of the conventional chromosome assay. And the fragment rate of chromosome condensation induced by Okadaic acid has a favorable linearity relationship with external radiation doses.