A magnetic immobilized glucoamylase has been prepared by adsorbing glucoamylase onto a magnetic collidal particle and cross-linking it with glutaraldehyde.The effects of different concentration of glutaraldehyde,pH of buffer,and the amount of glucoamylase on immobilization. The results showed that the activity of MIE was 17 095 U／g dry gel.The activity recovery was 63%. And some properties of magnetic immobilized and native glucoamylase such as optimum temperature、optimum pH and michaelis constant、stabilities to heat and operational stability were studied and compared.