Radiosensitivity was enhanced by EGFR inhibitor C225. SER calculation was carried out and we found that treatment with C225 significantly improved the biological effect of irradiation. The radiobiological parameters of C225-treated H-520 cells were D0 = 1.32, Dq = 0.19, N = 1.352, while those of irradiated H-520 cells were D0 = 1.82, Dq = 0.51, N = 1.81. Data were shown as Mean + SD (N = 4). One representative of three experiments with identical results was shown.