Nanomaterials open an alternative way for water disinfection. However, limitations such as aggregation, toxicity, and complex post-treatment block their practical application. In this study, an antibacterial silver/reduced graphene oxide (Ag/rGO) hydrogel consisting of controlled porous rGO network and well-dispersed Ag nanoparticle is synthesized by a facile hydrothermal reaction. Scanning electron microscopy, transmission electron microscope, X-ray diffraction, mercury porosimetry, and Fourier transform IR spectroscopy are employed to characterize the Ag/rGO hydrogel. The 3D structure of the rGO network serves as an excellent support for Ag nanoparticles. Disinfection experiments show that the Ag/rGO hydrogel exhibits good efficacy against Escherichia coli when used as a bactericidal filter driven by gravity. The mechanistic study indicates that bacteria cells are inactivated due to cell membrane damage induced by silver nanoparticles and rGO nanosheets when they flow through Ag/rGO hydrogel. Moreover, due to the retaining of Ag by rGO, the leaching level of silver from Ag/rGO hydrogel is considerably lower than the drinking water standard. This study sheds new light on designing antibacterial materials for point-of-use water disinfection application.