Based on the kinetic equations of polymerization proposed by T．Kagiya．a kinetie study on the polymerization of butadiene in hydrogenated gasoline with Ln (naph)3-Al(i-C4H9)3-Al(i-C4H9)2 Cl catalyst has been carried out．It was found that the rate of propagation is first order with respect to the con-centration Of both active center and monomer．Thus．the equation of the polymerization rate can be described as Rp=kp[C*][M]．In addition，the nature of the chain，such as cliain initiation，transfer and termina-tion were also examined．The initiation step is considered to be instantaneous at 20℃ and 50℃．but slow down at 0℃．The ratio of the rate constant of chain transfer reaction of alkyla．luminum compound to the rate constant of chain propagation is close to 1/90． The decrease in polymerization rate should be ascribed to the deactivation of the active centers at hi gher temperateure(e.g.，50℃)．The termination reaction is shown to be a bimolecular process．