The fabrication of ideal Ag-modified magnetic nanoparticles (MNPs) as a recyclable antibacterial agent that possesses good dispersibility, strong magnetic responsiveness, and high bactericidal activity is still a challenge. In this study, we described a simple polyethyleneimine (PEI)-assisted connection method for fabricating high-performance Au@Ag-loaded MNPs (Fe3O4-Au@Ag). The Fe3O4 cores are first modified with uniform PEI shell (2 nm) through self-assembly under sonication. And then, the negatively charged Au@Ag NPs with a uniform size of 5 nm are adsorbed on the surface of the Fe3O4 cores through electrostatic interaction. The Au@Ag-loaded MNPs were obtained within 30 min, and they were highly uniform in size and shape with good dispersibility and strong magnetic responsivity. With the aid of the magnetic core, the residual nanoparticles can be recycled from solution through an external magnetic field. These dense Au@Ag NPs acted as antibacterial satellites in highly active areas for Ag ion releasing and bacteria contacting. The Fe3O4-Au@AgMNPs exhibited good antibacterial activity against both Gram-negative and Gram-positive bacteria. Moreover, the antibacterial activity of Fe3O4-Au@AgMNPs was significantly improved by streptomycin antibiotic modification. Enhancement of the bactericidal efficiency of Fe3O4-Au@Ag-streptomycin revealed the presence of a synergistic effect between the MNPs and the introduced antibiotic.