In this work, a CoSb-nanocrystal/graphene hybrid nanostructure has been synthesized by a facile one-pot in situ solvothermal route. X-ray diffraction and X-ray photoelectron spectroscopy analyses show that the formation of CoSb alloy (CoSb or CoSb2) and the reduction of graphite oxide occur simultaneously during the one-pot solvothermal process. Scanning electron microscopy and transmission electron microscopy observations indicate that quasi-spheric CoSb (or CoSb2) nanoparticles with a size of 10–30nm are uniformly anchored on graphene, forming a unique layered structure. The presence of graphene prevents the nanoparticles from aggregating. The attached alloy nanoparticles also hinder the restacking of the graphene sheets. The electrochemical measurements have shown that CoSb-nanocrystal/graphene nanocomposites exhibit improved electrochemical Li-storage properties compared with bare CoSb alloy, due to the combined buffering, confining and conducting effects of the in situ introduced graphene.