The pyrocatechol sulfonephthalein (PS) modified glassy carbon (PS/GC) electrode, which was prepared by adsorption of PS on glassy carbon electrode surface, shows electrocatalytic activity toward NADH oxidation with an overpotential of ca. 310 mV lower than that of the bare electrode and a great enhancement of the anodic currents. The electrocatalytic rate constant (k) was determined using rotating disk electrode measurements in Britton-Robinson buffer solution at pH 7.0. It is found that the k is dependent on NADH concentration, the relation between k(-1) and c(NADH) can be fit to the line regression equation: 10(5) k(-1) (dm(3) mol(-1) s(-1))(-1) = 1.62286 + 0.65286c(NADH) (mmol dm(-3)) with correlation coefficient of 0.99964. The experimental results also indicate that the presence of Ca2+ and Mg2+ in electrolyte can drastically enhance the electrocatalytic currents of NADH oxidation.