Abstract: Kinetics on the polymerization of butadiene with MoCl₂(n-C₈H₁₇O)₂- (i-Bu)₂ AlOph as catalyst has been studied. The result shows that the polymerization is a first order reaction for both Mo(Ⅳ) catalyst arid monomer. The apparent activation energy for the polymerization is 18.5 Kcal mol^-1 and the preexponential factor 1.6 × 10¹⁰ min^-1. Some of the kinetic parameters, such as the efficiency of catalyst (α), the concentration of active center (P), and the meen lifetime of living polymer chain (τ) in different temperatures have been determined. This has proved that the time of equal rate polymerization (τ₀) is approximately equal to the lifetime of living polymer chain (τ).