The Ionic Liquid 1-butyl-3methyl-imidazolium bromide ([Bmim]Br) was found to be a good catalyst for the decomposition of Cumene Hydroperoxide(CHP) to ɑ,ɑ-Dimethylbenzyl alcohol(CA). The mechanism of [Bmim]Br-catalyzed conversion of CHP to CA has been studied using density functional theory(DFT) calculations. The DFT results showed that the Br anion of [Bmim]Br played a crucial role in the decomposition of CHP to CA. The energy barrier of [Bmim]Br-catalyzed decomposition of CHP is 21.4 kcal/mol. This research provides the feasibility of ionic liquid as catalysts for CHP decomposition to CA.