The composite material based on poly(oligo(ethylene glycol) methacrylate)-grafted-layered double hydroxides/Gentamicin (LDHs-g-POEGMA-GE) was prepared by the reversible addition fragmentation chain transfer polymerization, and its antibacterial property was investigated. Initially, the surface of LDHs was modified by S-(3-trimethoxysilyl) propyl trithiocarbonate as a chain transfer agent and then grafted with POEGMA. Subsequently, GE was covalently linked to the POEGMA chains by esterification reaction producing LDHs-g-POEGMA-GE. The composites were characterized by using FT-IR, GPC, XRD, TGA, and SEM analyses. The in-vitro assay with Staphylococcus aureus bacteria indicated the high antibacterial activity of the composites, which promises potential applications in the biomaterial field.