Magnetic Fe3O4 nanoparticles were synthesized by co-precipitation method and the mercaptopurine(MER) drug-loaded magnetic microspheres were obtained through emulsion cross-linking methods. The efficiency of this approach was evaluated in terms of drug loading content(DLC), encapsulation efficiency(EE) and delivery properties in vitro, determined by high performance liquid chromatograph(HPLC). The microspheres showed good DLC values of 11.8%, as well as good EE values of 79.4%. The in vitro drug release study was carried out in phosphate buffer solution(PBS) simulated body fluid, at 37 ℃ with pH=7.4. The release profiles showed an initial fast release rate, which decreased as time progressed and about 84 % had been released after 48 h. The experimental results indicated that the prepared magnetic microspheres may be useful for potential applications of MER for magnetically targeted chemotherapy. Magnetic Fe3O4 nanoparticles were synthesized by co-precipitation method and the mercaptopurine (MER) drug-loaded magnetic microspheres were obtained through emulsion cross-linking methods. The efficiency of this approach was evaluated in terms of drug loading content (DLC), encapsulation efficiency ( EE) and delivery properties in vitro, determined by high performance liquid chromatography (HPLC). The microspheres showed good DLC values ​​of 11.8%, as well as good EE values ​​of 79.4%. The in vitro drug release study was carried out in phosphate buffer solution (PBS) simulated body fluid at 37 ° C with pH = 7.4. The release profiles showed an initial fast release rate, which decreased as time progressed and about 84% had been released after 48 h. The experimental results indicated that the prepared magnetic microspheres may be useful for potential applications of MER for magnetically targeted chemotherapy.