Abstract: Quadripolymer of tris(monododecy ester maleate)lanthanum，N-cyclohexyl-malcimide，styrene，and methyl methacrylate was synthesized via emulsion copolymerization and employed in PVC to improve its heat resistance. When the amount of LaTM and N-cyclohexylmalcimide in copolymer was 5 and 9.5 wt %，respectively, and the loading of quadripolymcr in PVC was 20 wt%，the Vicat softenink temperature，the 1 % and 50 % weight loss temperature of the blends increased 4. 7℃，32.64℃，and 17 .31℃based on neat PVC，respectively. In addition，the tensile and impact strengths of the blends increased 3.35 % and 1.62 %，respectively.

Key words: poly(vinyl chloride), organic rare earth, V-cyclohexylmalcimide, heat resistance