Abstract: The catalytic behavior on the redox reaction of hydroquinone at 3 GCE′s modified separately with gold nanoparticles, carbon nanotubes and composite of gold nanoparticles and carbon nanotubes was studied by cyclic voltammetry. It was found that enhancement of electrochemical response of redox reaction of hydroquinone at either of the 3 modified electrodes was observed. As shown by the electrochemical impedance spectra and by the results of testing for effect by quantity of the nanomaterials modified on the GCE, the enhancing effect at the Au nano-particles modified electrode was due to the electrocatalytic action of gold nano-particles, while the enhancing effect at the carbon nanotubes modified electrode was due to electrocatalytic action of carbon nanotubes as well as large surface area of the electrode. As for the composite modified electrode with both the Au nanoparticles and the carbon nanotubes, it behaved to have the peculiarities of both the modifying nanomaterials. It was also found that the electrochemical reaction of hydroquinone at either of the 3 modified electrodes was controlled by diffusion process.