The invention belongs to the technical field of immobilization of enzymes and particularly relates to a method for preparing ginsenoside-Rd through immobilization of cellulase and enzymolysis of ginsenoside-Rb1 by virtue of a covalent cross-linking process. An immobilized enzyme is prepared through three steps of polyethyleneimine amination, glutaraldehyde cross-linking and enzyme immobilization. Compared with a manner of simply utilizing a free enzyme, the method has the advantages of recyclability, high selectivity, no pollution and the like. Compared with other enzyme immobilization methods, the method has many advantages that the bonding is firm, the operation is stable and the repeated utilization is realized, and the method is more suitable for industrial production.