The goal of the present investigation is to study the interaction of AgNPs with thymus DNA by traditional and original spectra-photometric and thermo-dynamic methods and approaches in darkness and under photo-irradiation. 1) At the interaction of DNA with nano-particles hypsochromic shift of 6 nm and hypochromic effect of 20% of AgNPs absorption band are observed. 2) At photo-irradiation (λ = 436 nm or full spectrum of visible band) of AgNPs-DNA complexes absorption spectra band width is changed from 140 nm to 360 nm at half-height. Besides, isosbestic point is observed. 3) Kinetic study of photo-diffusion has made it possible to determine desorption rate constant and desorption reaction activation energy that are equal respectively to k_d @ 9 ′ 10^-5 s^-1, E_d @ 80 kJ/M Ag⁰ for AgNPs bound with DNA. It is shown that AgNPs represent liquid drops which moisture the DNA surface at interaction. At photo-irradiation of AgNPs-DNA complex DNA dependant conformational transition takes place due to fast and intensive heating.