In this work, graphene and titanium dioxide nanoparticles nanocomposite modified glass carbon electrode (GR–TiO2/GCE) was developed to serve as a sensor for simultaneous determination of catechol (CC) and hydroquinone (HQ). The GR–TiO2 nanocomposite was characterized by using scanning electron microscopy and electrochemical impedance microscopy. The application of GR–TiO2 nanocomposite in simultaneous determination of CC and HQ was investigated by cyclic voltammetry and differential pulse voltammetry. The GR–TiO2 nanocomposites modified electrode displays excellent electrochemical catalytic activities toward CC and HQ, which could be attributed to high electrical conductivity and larger surface area of GR–TiO2 nanocomposites. The oxidation peak currents of CC and HQ were linear over the range of 0.5–100μM with the detection limits of 0.087μM for CC and 0.082μM for HQ, respectively. In addition, the modified sensor shows excellent anti-interference from resorcinol, phenol and nitrobenzol due to their different oxidation peak potentials. The proposed sensor was successfully applied in the simultaneous determination of CC and HQ in tap and lake water samples with satisfied results.