Abstract: Galvanostatic oxidation of glucose, galactose and ethanol at platinum electrodes in 0.5 mol•L^-1 aqueous NaOH and accompanying potential oscillation behaviors were comparatively studied by the electrochemical quartz crystal microbalance(EQCM) method. The EQCM-frequency oscillation was synchronously observed for the two saccharide systems during their potential oscillations, but it was negligibly small for the ethanol system, and the responses of the motional resistance were minor for all systems, suggesting that the mass effect verned the EQCM frequency responses. Although glucose and galactose are very similar in chemical structure and the amplitude for potential or frequency oscillation was roughly equivalent for both systems, the wave numbers and periods were obviously different from each other, implying that the electrochemical oscillation possesses high molecular recognition between the two systems. Related oscillation mechanism, the effect of NaOH concentration on oscillation, and the electrochemical process of platinum electrode in aqueous NaOH were also discussed. It was concluded that the platinum oxide formed here was mainly PtO₂-3H₂O_ad, and the potential oscillations for the two saccharide systems were accompanied with the adsorption/desorption of anions of saccharic acids at high/low potentials on platinum.