This disclosure relates to a method for preparing polyalkylenecarbonate. More specifically, in the method for preparing polyalkylenecarbonate, by using a solution polymerization with a specific heterogeneous catalyst and a solvent in the polymerization process of an epoxide compound and carbon dioxide, the products of side-reaction are reduced, removal of metal residues and by-products from the products is facilitated, danger due to overheating of the reactants is minimized, and heat removal and process stability are improved, and thus, high molecular weight copolymer may be easily provided, and mass production and scale-up are easy.