A simple, inexpensive, one-step synthesis of graphene/PAA-Au nanocomposites was achieved by using polyallylamine (PAA) as a reducing and stabilizing agent. The synthetic process was carried out only in aqueous solution, which is versatile and environmentally friendly. The resulting nanocomposites could be dispersed into water stably without any additional protection by polymeric or surfactant stabilizers. The products were further characterized by UV-visible absorption spectroscopy, transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR) and photoelectron spectroscopy (XPS). The results indicate that graphene sheets played an important role as a support material to increase the active area of Au nanoparticles (AuNPs). And the resulting graphene/PAA-Au nanocomposites film exhibited good electrocatalytical activity towards reduction of both H(2)O(2) and O(2), which showed potential application in electrochemical sensors.