In this work, a novel Ag/graphene composite was synthesized as a promising antibacterial agent. The high-quality graphene was prepared from the expandable graphite first and silver nanoparticles (Ag NPs) were then supported on the graphene sheets by a facile chemical reduction. TEM, SEM, and XPS characterizations show the crystalline of Ag NPs with a typical diameter of 45-50 nm are homogeneously decorated onto graphene sheets without aggregation. Furthermore, the antibacterial activity of composite is investigated using the agar well diffusion method. Results reveal the Ag/graphene composites exhibit outstanding and stable antibacterial activity against E. coli due to good dispersibility of Ag NPs and high-quality of graphene substrate.