Micron-sized flower-like porous Fe3O4 microparticles were fabricated by improved solvothermal method. Then, flexible dendrimer-grafted Fe3O4@SiO2-NH2/PAMAM microcarriers were obtained by functionalized modification of Michael addition and amidation process. The immobilization of penicillin G acylase on the carrier was realized by cross-linking of glutaraldehyde, and we investigated the optimum immobilization conditions. Under the optimal immobilized conditions, the reaction activity could reach 3098.96 U/g. When the reaction temperature was 47 A degrees C, the immobilized PGA had the highest activity of 394.74 U/g, which indicated that the immobilized PGA had better thermal stability than free PGA. The activity of immobilized enzyme maintained 82.14% after reused for nine times, which indicated that the immobilized enzyme had good stability and good industrial application potential.