The copolymerization of BF2-omplexed ethyl acrylate with propylene in the presence ofAIBN at 25℃ was investigated. It was found that the rate of the copolymerization was propor-tional to the square root of the initiator concentration. The chain transfer agent CCl4 greatly af-fects the inherent viscosity of the resulting copolymer. The smaller the dielectric constant of thesolvent, the greater the rate of copolymerization is. The equal concentration of the two monomers give the maximum copolymerization rate.The 1H-NMR and 13C-NMR analysis indicated,when [EA·BF3]/[EA·BF2]+[P]>0.5,the resulting copolymer was the acrylate-rich random copolymer.Through the linetic experiments we suggest that copolymerization follows the mechanism of the random copolymerization of the ternary complex with binary complex.When [EA·BF3]/[EA·BF3]+[P]≤0.5,the resulting copolymer is always strictly alternatin,and the alternating copolymerization follows the mechanism of the ternary complex homopolymerization.Using the homolog of the proptlene,1-pentene,we found that BF2-complexed ethyl carylate can form a ternary complex with 1-pentene identified by UV spectroscopy.This is a strong evidence for the mechanism of ternary complex homopolymerization.