Copolymerzation of proplene oxide and carbon dioside was successfully carried out by using new rare-earth catalytic systems for the first time. It has been found that ternary rare-earth coordination catalysts composed of rare-earth phosphonat, triisobutylaluminum, and glycerine are effective catalysts for the copolymerixation. The system Y(P204)3-Al(i-Bu)3-glycerine shows the highest activity. The yield and interinsic viscosity of the copolymer depend significantly on the molar ratio of catalyst components and the reaction condition. The copolymers prepared were characterizaed by IR, 1HNMR, GPC. and DTA-TGA. It is showed that the copolymers obtained have a high molecular weight with a narrow molecular weithg distribution is showed that the copo;ymers obtained have a high molecular weitht with a narrow molecular weith distribution and a high thernmal stsbility. The carbonat unit content of the methanol-insoluble copolymer is as high as 30-40%.