Abstract: Objective: To observe the injury of OS-732 cell line caused by radiation combined fast neutron with photon. Methods: We tested the clone forming rate of the OS-732 cell line after irradiated by fast neutron,photon and the mixed beam（fast neutron plus photon）. Results: The inhibition effect of the clone forming was weaker in the groups of mixed beam than that in the group of fast neutron and photon alone after 10 days. Conclusion: The killing effect was powerful to the OS-732 cell line in the fast neutron alone group and photon alone after 10 days. The studies provide an experimental research for the treatment of osteosarcoma.