Co-graphene composites were prepared by a simple one-step method using glucose as carbon source, NH4Cl as blowing agent and nano-metal Co as catalysts for promoting graphitization of glucose. The formation of graphene and the in-situ growth of Co nanoparticles are simultaneously performed. The structure and morphology of the composites were characterized by XRD, FTIR, XPS, Raman, UV-Visand and TEM. The composite was applied to catalytic reduction of p-nitrophenol (4-NP) and the results showed that 4-NP was completely reduced in 8 min using 4 mg catalyst at room temperature. It can be recycled by simple magnetic separation and has good cycle stability.