Abstract: An unsaturated xylofuranose, 4-mehtylene-1, 2-0-isopropylidene-3-methoxy-α-D-xylofu ranose(11) is synthesized. The structural analyses using IR, ¹H-and ¹³C-NMR iodicate that a copolymer with addition and ring-opened units were obtained. Upon the structures of polymer, a propagation mechanism was proposed. The polymerization activity, propagation mechanism and polymer structures between the frec radical and cationic polymerization of the unsaturated xylofuranose were discussed.