Abstract: The kinetics of the induction period in the polymerization of 1-octene catalyzed by Solvay TiCl₃-alkyl aluminium was studied with a dilatometer. The induction period decreases as [TiCl₃] and [M]₀ increase and temperature rises. It was observed through a microscope that large catalyst particles broke up into small particles in the induction period. So a kinetic model was proposed which ascribes the induction period to the breaking up of catalyst particles under the effect of polymer, and the most of the experimental results can be explained on the basis of the model.