Magnetic agarose microsphere was prepared by reverse-phase microemulsion method, and its surface was modified with epoxy groups to immobilize angiotensin converting enzyme (ACE). The factors that influence the immobilization of ACE were investigated. The optimum immobilization conditions were: ACE concentration of 8 mg/mL，pH=7.8，temperature 50℃, immobilization time of 2h, with a optimal specific activity of 0.128 U/g spheres. The properties of magnetic immobilized ACE were studied. The optimal catalytic pH of the immobilized ACE was 8.3 and the optimal temperature was 42℃. The pH tolerance and thermal stability of the magnetic immobilized ACE and free ACE were also evaluated, the enzyme activity retention rate after keeping at pH=5 for 1h were 62.1% and 40.7%, respectively, and the retention rate were 95.7% and 89.2% at pH=9. The immobilized enzyme still kept 50.2% of the original activity at 60 ℃, as the compared with the free enzyme was 20.7%. After 30 days storage at -20℃, the immobilized ACE activity remained 90.3%. 53.0% of the initial activity remained after recycled for 10 times. The result shows that magnetic immobilized ACE has a good application prospect due to its quick repeated recycling under an additional magnetic field.