Epoxy propyl methacrylate or epoxy propyl acrylate is polymerized and the polymer is then grafted with cellulose and finally ring-opening reacted to obtain affinity medium whose active group is aldehyde group or amino group. The polymerization and graft reaction are carried out in neutral medium with reaction temperature being 50-100 deg.c and the ring-opening reaction of amino group is at 40-80 deg.c. The affinity medium thus prepared has high bonded cellulose capacity and may be widely used in large-scale separation and purification of biological product and body's immunity treatment.