Abstract: In this paper the contents of academic exchange in 2^nd international conference of 《the effects of low and very low doses of ionizing radiation on human health》are introduced. The description is divided into four main parts. LDR inducing hormesis and adaptive response are showed by experiment and epidemiologic investigation. Its clinical application is presented.Validity of permitted dose of ionizing radiation is evaluated by varied outcomes. During 15 years after Chernobyl accident many reports of epidemiologic investigation are advanced to reflect the relation between the radiation dose and effect. Linear no-threshold theory is argued.