PURPOSE: To provide the titled compsn. having excellent impact resistance, by blending a specified treated olefin polymer with a propylene/ethylene block copolymer.

CONSTITUTION: A carboxylic acid-contg. olefin polymer (a) obtd. by reacting an unsaturated carboxylic acid (anhydride) such as maleic anhydride or acrylic acid with an olefin polymer such as ethylene polymer, propylene polymer or their copolymer having an MW of 20,000W100,000, and a polar group-contg. olefin polymer (b) obtd. by reacting an unsaturated org. compd. having at least one polar group selected from hydroxyl, amino and glycidyl groups, such as 3- hydroxy-1-propene, with an olefin polymer, are melt-mixed together to form a treated olefin polymer. 1W30wt% said treated olefin polymer is blended with a propylene/ethylene block copolymer having an ethylene content of 1W30wt% and a melt flow index of 0.01W100g/10min.