The interaction of the two new synthesized transition-metal complexes, ML 2 (M=Co, Cu, L=1,8-dihydroxyethyl-1, 3,8,10,13-hexa-azacyclotetradecane) with calf thymus DNA was probed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Adding deoxyribonucleic acid (DNA) into [CoL] 2 + and [CuL] 2 + solution, the i p value of all the peaks of [CoL] 2 + and [CuL] 2 + significantly decreased in proportion to concentration of DNA. Glassy carbon electrodes (GCEs) were modified with DNA by adsorption, and it was electrochemically characterized with transition-metal complexes, [ML] 2 + . The DNA modification layer on the GCE is unstable to alkali and to heat, but stable to acid solutions and very stable in long stock in a dry state. It could be seen that peak potential shifted positively and the peak current increased significantly. The electrochemical parameters, binding constant (k n + ) and binding sites(s) were calculated by a nonlinear regression method.