A novel method for preparation of polymer-based magnetic microspheres was proposed by utilizing melt reactive blending, which was based on selective location of Fe3O4 nanoparticles in PA6 domain of polystyrene (PS)/polyamide 6 (PA6) immiscible blends. The results showed that most of Fe3O4 was located in the PA6 microspheres. Magnetization data revealed the magnetite content of PA6/Fe3O4 microsphere could be up to 54 wt % with strong magnetic responsibility and high saturation magnetization. Carboxyl functional group, bonded with PA6/Fe3O4 microsphere by copolymerization of acrylic acid with PA6 chain in different concentration ethanoic acid (HAc) solution, was used as a ligand for protein adsorption. The amount of adsorbed bovine serum albumin (BSA) was optimized by changing the medium pH and the initial concentrations of BSA. The results denoted that the adsorption capacity of BSA reaches 215 mg/g microspheres, showing potentials to promising applications in bioseparation and biomedical fields. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 2271-2277, 2011