Alterations of mitochondria DNA(mtDNA)4977 bp common deletion(CD)and mtDNA copy number induced by ionizing radiation were observed in human different cell lines and total body irradiation patients.However,only few experiments have evaluated the levels of the CD and mtDNA copy number in human peripheral blood exposed to ionizing radiation till now.The aim of this study is to analyze the mtDNA alterations in irradiated human peripheral blood from healthy donors as well as to explore their feasibility as biomarkers for constructing new biodosimeter.Peripheral blood samples were collected from six healthy donors,and exposed to 60Co gamma ray with the doses of 0 Gy,1 Gy,2 Gy,3 Gy,4 Gy and 5 Gy.Levels of the CD and mtDNA copy number in irradiated samples after 2h or 24h incubation were detected using TaqMan real-time PCR,and the CD ratio was calculated.The results showed that the mean of the CD ratio and the CD copy number exhibited a dose-dependent increase 2 h in the dose range from 0–5 Gy,and of the mtDNA copy number significantly increased 24 h in irradiated groups compared with 0 Gy group after irradiation.It indicates that the parameters in human peripheral blood may be considered as molecular biomarkers to applying construction of new biodosimeter. Alterations of mitochondria DNA (mtDNA) 4977 bp common deletion (CD) and mtDNA copy number induced by ionizing radiation were observed in human different cell lines and total body irradiation patients. However, only few experiment have evaluated the levels of the CD and mtDNA copy number in human peripheral blood exposed to ionizing radiation till now. The aim of this study is to analyze the mtDNA alterations in irradiated human peripheral blood from healthy donors as well as to explore their feasibility as biomarkers for constructing new biodosimeter. Peripheral blood samples were collected from six healthy donors, and exposed to 60Co gamma ray with the doses of 0 Gy, 1 Gy, 2 Gy, 3 Gy, 4 Gy and 5 Gy. Levels of the CD and mtDNA copy number in irradiated samples after 2h or 24h incubation were detected using TaqMan real-time PCR, and the CD ratio was calculated. The results showed that the mean of the CD ratio and the CD copy number exhibited a dose-dependent increase 2 h in the dose range from 0-5 Gy, and of the mtDNA copy number significantly increased 24 h in irradiated groups compared with 0 Gy group after irradiation. It indicates that the parameters in human peripheral blood may be considered as molecular biomarkers to applying construction of new biodosimeter.