Regenerated cellulose microspheres (RCS) were successfully prepared by using the sol-gel transition (SGT) method from cellulose drops in 7 wt% NaOH/12 wt% urea aqueous solution precooled to −12 °C. Subsequently, novel magnetic Fe₃O₄/cellulose microspheres (MRCS) were fabricated by in situ synthesis of Fe₃O₄nanoparticles into the cellulose pores of RCS, which were used as the solid template microreactor. Their structure and morphology were analysed using optical photomicrographs, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results indicated that the spherical magnetic Fe₃O₄nanoparticles were dispersed uniformly and immobilized in the cellulose matrix, and the structure and nature of Fe₃O₄ were conserved perfectly. The magnetometric measurements revealed that the MRCS exhibited sensitive magnetic-induced delivery, and had extremely small hysteresis loop and low coercivity. Moreover, MRCS displayed excellent adsorption and controlled release capabilities on bovine serum albumin (BSA). The Fe₃O₄nanoparticles in the cellulose microspheres play an important role in both the creation of the magnetic-induced transference and the improvement of the targeting protein delivery and release. It will be important for applications in the biomaterials field.