In the present paper, we demonstrated a facile one-step and effective electrochemical strategy to synthesize graphene/NiO nanocomposites, which represents a new type of graphene/transition metal complex heterostructure. For the electrochemical deposition at the potential range of −1.2 to 0V, graphite oxide (GO) was electrochemically reduced to graphene, accompanied by the simultaneous formation of NiO with a nanoparticle morphology. The obtained nanocomposites were characterized by scanning electron microscopy and electrochemical techniques. It was found that a large amount of NiO nanoparticles with diameter of 100–200nm were uniformly grown on both sides of graphene nanosheets. Electrochemical experiments indicated that the composite film had a large surface area and enhanced electron-transfer rate compared with only NiO nanoparticles, due to an efficient electrical network through NiO nanoparticles direct anchoring on the surface of graphene. Moreover, as a model, glucose and methanol were selected as small molecules to investigate the electrocatalytic properties of the nanocomposites. The results showed that an enhanced electrocatalytic performance of the nanocomposites was obtained. The nanocomposites based sensor exhibited a rapid and highly sensitive response to glucose and methanol, which might find promising applications in medical applications, biological fuel cells and food industries.