In this work, graphene/prussian blue (PB) composite nanosheets with good dispersibility in aqueous solutions have been synthesized by mixing ferric-(III) chloride and potassium ferricyanide in the presence of graphene under ambient conditions Transmission electron microscopy (TEM) shows that the average size of the as-synthesized PB nanoparticles on the surface of graphene nanosheets is about 20 nm. Foul er-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) patterns have been used to characterize the chemical composition of the obtained graphene/PB composite nanosheets. The graphene/PB composite nanosheets exhibit good electrocatalytic behavior to detection of H2O2 at an applied potential of -005 V. The sensor shows a good linear dependence on H2O2 concentration in the range of 0.02-0 2 mM with a sensitivity of 196 6 mu A mM(-1) cm(-2) The detection limit is 1 9 mu M at the signal-to-noise ratio of 3 Furthermore, the graphene/PB modified electrode exhibits freedom of interference from other co-existing electroactive species This work provides a new kind of composite modified electrode for amperometric biosensors (C) 2010 Elsevier Ltd All rights reserved.