Bacterial cellulose (BC) is a biosynthesized carbohydrate polymer with excellent biocompatibility and water holding capability. However, it lacks an inherent antibacterial activity that has limited its in-depth biomedical applications. This study investigated a novel strategy of adopting a simultaneous process to chemically anchor a quaternary ammonium salt (R-N(CH3)+) with a special vinyl group (2-methacryloyloxyethyl trimethylammonium chloride, METAC) onto the BC, and meanwhile, enhance the density of (R-N(CH3)+) via free radical vinyl polymerization. The results have confirmed the transition of BC surface from a negatively-charged surface to a polycationic surface via such a simultaneous reaction. As compared to chitin film (a representative of R-NH3+), the resulting METAC-grafted BC (a representative of high-density R- N(CH3)+) acquired excellent water absorbability (40 times of dry weight of the BC), 99% antibacterial activity against Escherichia coli and Staphylococcus aureus, a satisfactory in-vitro biocompatibility, and a better in-vivo wound healing outcome with an excellent in-vivo antibacterial efficacy. This study has exhibited potential in utilizing a facile method to prepare a bio-safe, adaptive antibacterial surface for various biomedical applications.