As a means for the chemical fixation of carbon dioxide and the synthesis of biodegradable polycarbonates, copolymerizations of carbon dioxide with various epoxides such as cyclohexene oxide (CHO), cyclopetene oxide, 4‐vinyl‐1‐cyclohexene‐1,2epoxide, phenyl glycidyl ether, allyl glycidyl ether, propylene oxide, butene oxide, hexene oxide, octene oxide, and 1‐chloro‐2,3‐epoxypropane were investigated in the presence of a double metal cyanide catalyst (DMC). The DMC catalyst was prepared by reacting K3Co(CN)6 with ZnCl2, together with tertiary butyl alcohol and poly(tetramethylene ether glycol) as complexing reagents and was characterized by various spectroscopic methods. The DMC catalyst showed high activity (526.2 g‐polymer/g‐Zn atom) for CHO/CO2 (PCO2 = 140 psi) copolymerization at 80 °C, to yield biodegradable aliphatic polycarbonates of narrow polydispersity (Mw/Mn = 1.67) and moderate molecular weight (Mn = 8900). The DMC catalyst also showed high activities with different CO2 reactivities for other epoxides to yield various aliphatic polycarbonates with narrow polydispersity.