A composite material Ti/SIL was prepared by Ti(OC4H9)(4) coordinating to imidazolium ionic liquid grafted on SBA-15 and characterized by FT-IR, XRD, TEM, XPS, NH3-TPD and N-2 adsorption-desorption technique. The catalytic performance of the prepared Ti/SIL for solvent-free oxidation of alpha-methylstyrene (AMS) to acetophenone using H2O2 oxidant was evaluated, achieving high TOF (23.2 h(-1)). The adsorption behavior of AMS via interaction with Ti4+ and Si-O active sites on the catalyst surface was measured by in situ DRIFTS, Si-29 CP MAS NMR spectroscopy and analyzed by DFT theoretical calculation. Based on these analysis results, the reaction mechanism, involving the activation, consecutive conversion of AMS and homolytic decomposition of H2O2 on the catalyst surface to generate the product was proposed. Graphic An interaction between Ti4+ and Si-OH active sites were found on the catalyst surface of TiO2 dispersed on imidazolium ionic liquid grafted SBA-15 by in-situ DRIFTS and 29 Si CP MAS NMR spectra analysis, which was responsible for the activation of AMS molecules. The generation of the surface active intermediate and homolytic cleavage of H2O2 molecules were well confirmed by DFT theoretical calculation. Based on these results, the reaction mechanism was proposed.