In order to investigate the effects of ionizing radiation on MC3T3 cells’ proliferation and expression changes of Notch1 and Jagged1 genes, MC3T3 cells were exposed to γ-rays with 0, 2 and 4 Gy, respectively. MTT assay and real-time PCR were adopted to detect the proliferation of MC3T3 cells and the changes of expression of Notch1 and Jagged1 genes which could be in association with proliferation and differentiation. When exposed to 2 and 4 Gy γ-rays irradiation, the MC3T3 cells' proliferation reduced (p<0.01, p<0.01). The expression of Notch1 decreased when treated with 2 Gy irradiation (p<0.05). The expression of Jagged1 regulated down when given 2 and 4 Gy irradiation (p<0.01, p<0.05). Irradiated MC3T3 cells’ proliferation potentialities reduced and Notch1 and Jagged1were regulated down.Cited