The development of a highly effective and recyclable antibacterial agent is of great interest. In this work, magnetic Fe3O4/Ag antibacterial nanoagent was successfully fabricated through a facile surface functionalization approach. Utilizing the strong interaction between silver and the amino groups on the surface of Fe3O4 nanospheres, the nanosized silver particles were tightly bonded on the Fe3O4 nanospheres' surface, improving silver nanoparticals' antibacterial activity by preventing agglomeration of silver nanoparticles. Our antibacterial tests showed that the as-synthesized Fe3O4/Ag nanospheres presented high antibacterial performance against Gram-negative and Gram-positive bacteria. Moreover, these antibacterial nanohybrids can be easily recycled from water solution by applying an external magnetic field. Overall, taking into consideration the facile preparation method, excellent antibacterial activity and high magnetic recycling property, the as-synthesized Fe3O4/Ag nanospheres have great potential applications in medicine and water disinfection.