Dinuclear cobalt complex salen[Co(III)TFA]2 (salen = 3,5-di-tert-butyl- salicylaldehyde-3,3ˊ-diaminobiphenylamine, TFA = trifluoroacetic acid) was synthesized and used to catalyze the preparation of novel polycarbonate terpolymers (PPCEA) of carbon dioxide, propylene oxide and norbornene dianhydride. The results showed high catalyst reactivity under mild conditions, generating a polymer with maximum Mn of 2.3 × 105 g/mol and a narrow molecular weight distribution PDI of 1.01. The 5% thermal weight loss temperature (Td,-5%) of PPCEA can reach 310 °C, which is 150 °C higher than conventional polypropylene carbonate. In addition, its mechanical properties were also improved. The tensile strength increased from10.8 MPa to 22.8 MPa, and elongation at break decreased from 430% to 106%. The polymer has good degradability as well. Furthermore, based on the polymerization results, the corresponding polymerization mechanism is proposed in this paper.