Abstract: Methods and criteria for the identification of male individual radiosensitivity are investigated. The peripheral blood of 50 male volunteers was irradiated with different doses of X-ray, the micronucleus frequency(MNF) was measured by cytokinesis-B block micronucleus assay, and the central standard curve of micronucleus dose effect was drawn by second-order multinomial fitting method so that the individual dose-response curve of micronucleus was compared with the standard curve to judge individual radiosensitivity. In the dose range of 0.0~2.5 Gy, the central equation of second-order polynomial fit for dose effect is (MNF=0.014 7+0.036 2D+0.023 1D ², R=0.726). Among the 50 male volunteers, 13 were sensitive to radiation (26.0%) and 14 were resistant (28.0%), which basically fits the normal distribution. Spearman rank correlation analysis showed that the MNF increased with the dose and there was a positive correlation between the background MNF and the radiosensitivity of each dose, but negative correlation with the radioresistance. In conclusion, a "curve-instead-of-dose" male individual radiosensitivity identification method was established. Moreover, it was found that the background of micronuclei in peripheral blood lymphocytes was positively correlated with individual radiosensitivity.