PURPOSE: To produce a linear copolymer by bringing carbon monoxide into contact with at least one olefinically unsatd. compd. in the presence of a catalyst compsn. contg. a Pd source and an anionic phosphorus monodentate ligand.

CONSTITUTION: A catalyst compsn. contg. a Pd source and an anionic phosphorus monodentate ligand represented by the formula: R1R2P-R-X (wherein R1 and R2 are each hydrocarbyl; R is a divalent bridging group; and X is an anion) and derived from an acid having a pK lower than 4, in an amt. corresponding to 10-7-10-3 g-atom of Pd per mol of the olefinically unsatd. compd. being copolymerized, is charged together with a diluent (e.g. methanol or diglyme) into an autoclave. Then, carbon monoxide and an olefinically unsatd. compd. (e.g. ethene) in a molar ratio of (1/30)-(1/3) are charged into the autoclave and copolymerized at 20-200°C under 1-200 bar, giving a random copolymer having olefin-derived monomer units and carbon monoxide-derived monomer units in a molar ratio of (52.5/47.5)-(80/20) and 10-50 wt.% terminal homopolymer blocks.