Objective To improve the immobilization technology of bromelain which has poor stability to enhance its utilization, stability, and storage performance.Methods The preparation process of magnetic chitosan/sodium alginate immobilized bromelain (Fe₃O₄-SA/CS-Br) is optimized by the response surface methodology. The Fe₃O₄-SA/CS-Br is characterized and its K_m value, operational stability, thermal stability, storage stability, and application effectiveness are determined.Results The optimal preparation conditions for Fe₃O₄-SA/CS-Br are as follows: m_chitosan∶m_{sodium alginate} ratio of 1∶4, Fe₃O₄ mass concentration of 10 mg/mL, CaCl₂ mass concentration of 32 mg/mL, immobilization time of 106 min, pH value of 7.0, and enzyme mass concentration of 1.0 mg/mL. According to the results from scanning electron microscopy, infrared spectrum, and X-ray diffraction spectrum, the main functional groups of bromelain are successfully immobilized on Fe₃O₄-chitosan/sodium alginate (Fe₃O₄-SA/CS) microspheres. The affinity of bromelain for the substrate is enhanced after immobilization.Conclusion Fe₃O₄-SA/CS-Br can effectively enhance the stability of bromelain.