Abstract: Advanced antimicrobial agents that treat infectious diseases are greatly needed. Various silver-based nanomaterials have been developed and are considered potential candidates for many commercial products, but they lack durability and adequate antibacterial activity. A new class of nanohybrids of silver nanoparticles (AgNPs) grown in-situ on graphene oxide (GO) using a silver ion salt was synthesized by a simple ultrasonic mixing method. The structure and composition of the nanohybrids were investigated by SEM, TEM, FTIR, TGA, XRD and XPS. Results indicated that GO acts not only as a negatively charged macromolecule for capturing Ag⁺ ions, but also a reducing agent to reduce the Ag⁺ ions to AgNPs. The heterogeneous structure leads to abundant well-dispersed AgNPs and Ag⁺ ions on the GO support. The as-prepared nanohybrids make full use of the advantages of both AgNPs and GO-Ag⁺ salts, leading to improved and long-term antibacterial activity against both S.aureus and E. coli.