The submicron-sized Fe₃O₄ particles were synthesized by solvothermal method. Then polydopamine (PDA) was used to modify the surface of Fe₃O₄ particles. And then the core-shell Fe₃O₄@PDA@BSA (single layer and multilayer) microspheres were prepared by the layer by layer self-assembly method (SAM). In addition, Ag nanospheres were grafted onto the surface of Fe₃O₄@PDA particles to obtain Fe₃O₄@PDA-Ag core-shell nanoparticles using silver mirror reaction. The morphology and component of the obtained core-shell particles were characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The biocompatibility of the microspheres was researched in vitro by MTT method and its magnetic properties were also evaluated. The results showed that the microsphere has excellent magnetic properties and good biological safety. Then the catalytic performance of Fe₃O₄@PDA-Ag microspheres for methylene blue (MB) was studied. And the antimicrobial properties of Fe₃O₄@PDA-Ag microspheres for Escherichia coli and Bacillus subtilis were also be discussed. The results indicated good catalytic properties and antibacterial properties.