Abstract: This work presents new insight in the initiating mechanism of the anionic polymerization based on the anionic bulkpolymerization of styrene (St) at the temperature ranging from 60°C to 140 °C. The results revealed that the inactive aggregation of n-butyllithium existing in a hexameric structure at low temperature (<20 °C) could be transformed into the active species at high temperature (≥60 °C). It was found that there were 1.3 active positions in average randomly distributed in the hexamericstructure, which could initiate the polymerization of St. The polymer coils in the hexamericstructure could block the diffusion of the monomers into the ionpairs and result in a stationaryconversion platform (SCP) with a relatively long duration. The increase of temperature seemed to shorten the duration of SCP due to timetemperature equivalence principle, thus accelerating the polymerization significantly. Then, the aggregates were dissociated completely into 6 equal polystyryllithium macromolecules, and the polymerization continued again and completed rapidly. The addition of polar regulator (THF) into the system significantly accelerated the polymerization rate only by shortening SCP, not by changing the aggregation structure of n-butyllithium.