Among the biological effects, radiation carcinogenesis is the most worrying problem. However, up to now, only large-dose-radiation is proved to have strong correlation to cancer induction; the data mainly base upon the long-term follow up of A-bomb survivors in Japan and the research work is majorly for cancers with high association to radiation, such as leukemia, thyroid carcinoma, lung cancer and breast cancer. As for professional exposure, usually chronic accumulation of small dose of radiation, there is few data by large case number and strict study model; therefore, no agreement at this point is got and it sill waits for further reserch.