By Schotten-Baumann's esterification of poly(2-hydroxyethyl methacrylate) with 10-undecenoyl chloride a new multimonomer -poly[2-(10-undecenoyloxy)ethyl methacrylate] was prepared. Based on the results of elemental analysis, FTIR, H-1-NMR and C-13-NMR spectra, the structure of the multimonomer was proposed. The thermal properties of the multimonomer were studied by DSC and TG. The rate of disappearance of double bonds in the multimonomer during UV irradiation was examined in the solid state to obtain a crosslinked product.