The fabrication of poly (2,6-pyridinedicarboxylic acid)/MWNTs modified glass electrode (PPDA/MWNTs/GCE) was proposed and used for individual or simultaneous determination of guanine and adenine. The performances of the PPDA/MWNTs/GCE were characterized with cyclic voltammetry (CV). The modified electrode exhibited enhanced electrocatalytic behavior and good stability for the detection of guanine and adenine. Differential pulse voltammetry (DPV) was used to determine the concentration of guanine, adenine. The detection limit (S/N = 3) for guanine and adenine was 0.045 μmol/L and 0.05 μmol/L, respectively. The electrochemical method for the measurement of guanine and adenine in calf thymus DNA was also developed with this modified electrode and the result was satisfactory.