Ag@Graphene nano-composite was prepared by one step in situ synthetic method, using polyethylene glycol as reductant. Graphene oxide and silver ions were reduced at the same time under hydrothermal reaction. UV-vis spectroscopy, X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM) were used to characterize the as-prepared nano-composite. The results of characterization indicated that silver nanoparticles were uniformly anchored on the surface of graphene sheets and the average particle size was 30nm. Antibacterial activity was tested using E. coli as model strain. The minimal inhibitory concentration of Ag@graphene against E. coil was 100µg/mL, making the composite an outstanding and novel antibacterial material.