DNA damages are the main cause of radiation-induced cell death, mutations and carcinogenesis. The study of influence of environmental conditions on the radiation damage of DNA structure is important for the wide range of medical problems. The present work is devoted to the study of alterations in DNA structure caused by γ-irradiation at the variation of counterions concentration and dose rate.The DNA solutions of the ionic strengths 0.005M and 0.15M NaCl were exposed to γ-radiation with the doses of 0-100 Gy, dose rates2.3Gy/s and 0.3 Gy/s. The lesions in DNA structure (base damages, partial denaturation) were studied by the methods of UV absorption spectroscopy and DNA melting.Radiation-induced base damages decrease at the rise of NaCl concentration in the solution and at the lowering of the dose rate. The stability of DNA secondary structure increase at the rise of ionic strength of irradiated solution. The influence of radiation dose rate on the DNA helicity reveals definitely only at the dose of 100 Gy. The relative fall of the DNA melting temperatureafter the irradiation slightly depends on the dose rate and NaCl concentration.