Quantitative analysis of dihydroxybenzene isomers holds great significance to agricultural chemistry, food safety and environmental protection. In this work, we demonstrate a facile strategy to determine catechol and hydroquinone by using acetylene black and gold nanoparticle composite modified electrodes (Au/AB/GCE). Compared with bare glassy carbon electrode (GCE), Au/AB/GCE showed much better performance in electrocatalytic oxidation-reduction of catechol and hydroquinone. The linear correlation between the peak currents and analyte concentrations suggested the simultaneous detection with ultralow limits of detection (0.5 μM and 1 μM for catechol and hydroquinone, respectively). Besides, the determination is selective and out of interference of common inorganic ions and organic compounds. Anson equation was employed to make a reasonable hypothesis, that the increased surface area and electrical conductivity of Au/AB/GCE contributed these good results. This strategy may become a promising means for ratiometric and simultaneous detection of catechol and hydroquinone in water with convenience and high sensitivity.