The invention provides a method for modifying the brittleness of carbon dioxide-cyclohexene oxide copolymers. The method comprises the following steps of: taking 40 to 90 portions of carbon dioxide-cyclohexene oxide copolymers, 8 to 48 portions of elastic elements, and 2 to 12 portions of terpolymers of acrylonitrile-styrene-acrylic acid, according to weight portion; uniformly mixing the carbon dioxide-cyclohexene oxide copolymers, the elastic elements and the terpolymers of acrylonitrile-styrene-acrylic acid in solvent, or in a Banbury mixer or in a double-screw extruder; and drying the mixture to acquire blends with improved brittleness. The method improves the brittleness of the carbon dioxide-cyclohexene oxide copolymers, maintains the tensile-strength over 30 MPa, improves the elongation even up to over multiple times, and maintains a high vitrification temperature of PCHC.