Abstract: The magnetic microspheres were prepared with Fe3O4 magnetic nucleus and sodium alginate-gelatin.Pectinase was immobilized while magnetic microspheres were crosslinked with glutaraldehyde. The preparation conditions of immobilized pectinase were optimized through orthogonal experiments based on single factor,and the properties of immobilized enzyme were investigated. The results showed that Fe3O4 magnetic nucleus could be made out when Fe2+(5mol/L)∶Fe3+(5mol/L) was 0.75∶1(volume ratio). When sodium alginate(3.5%)∶gelatin(3.0%) was 2.5 ∶1(volume ratio),the concentration of Fe3O4 magnetic nucleus was 3.0 miligram per millilitre,crosslinked with volume fraction of 4.0% glutaraldehyde for 2.5 hours,and following mixed with 20 miligram pectinase per gram supporter,the process time was one hour,p H value for 4.0,the recovery rate of immobilized pectinase activity could reach to 78.69%. The optimum p H and optimum temperature of immobilized pectinase for the hydrolysis of pectin were determined to be p H4.0 and 50℃,respectively. The immobilized pectinase was stable in a p H range from 3.0 to 7.0 and at temperature 20 ~55℃. The apparent Michaelis constant of immobilized pectinase Kmappequaled to 3.162mg/m L. The relative activity of immobilized enzyme remained 51.0% after continuous use for ten times,and that of remaining 81% after stored ten days. The results indicated the immobilized pectinase prepared with composite support were good enough for the strength,the flexibility and the recovery rate,and had good operation stability.