Objective: U251 cells were exposed to fast neutrons of 14 MeV energy, and dose-response relationships were derived; Methods:cell samples were exposed to fast neutrons. Radiation doses were 1 Gy, 3 Gy, 5 Gy and 7 Gy respectively. The cell survival, apoptotic rate and proliferation were tested after irradiation; Result: with the growth of the radiation dose, cell survival was declined, and apoptotic rate was promoted; the speed of the cell proliferation, which was observed 48 h after irradiation, was slowed down viously; Conclusion: compared to γ ray, fast neutrons have higher relative biological effectiveness.