Abstract: The catalytic activities of various chlorp-vanadates-triispbutylalumin-ium systems in alternating copolymerization of butadiene and propylene have been compared. It was found that the catalyst system consisted of neopentylchlorovanadate-triisobutylaluminium can give .high molecular weight alternating copolymers of butadiene and propylene in high yield.The character and behavior of the alternating copolymerization and the ways for increasing [η] of the copolymer have also been studied.Thus an alternating copolymer of butadiene and propylene .with inherentviscosity 1.7-2.6 dl/g was obtained at -76--45℃, the conversion ofwhich was more than 80%.The resulting copolymers were analyzed by IR and NMR, it was demonstrated that the alternating degree of the copolymers was about 95% and the content of trans-1,4 butadiene unit in the copolymers was above