In order to develop a highly efficient solid catalyst system, the ionic liquid is introduced into mesoporous molecular sieves of Al-MCM-41. Under the hydrothermal condition, the mesoporous molecular sieves of Al-MCM-41 are synthesized, to prepare the supported catalyst, dipped in the ionic liquid. The product is further characterized by FT-IR, TG, N₂ adsorp/desorp and elemental analyses. It is shown that the ionic liquid is grafted into the mesoporous molecular sieves of Al-MCM-41 successfully. The optimum reaction conditions are determined by the process of the orthogonal experimental design. Under the optimized reaction conditions, it is shown that when the molar ratio of benzene/olefin is 8:1, at the temperature of 200℃, with airspeed of 1.5h^-1 and pressure of 3 MPa, the conversion rate of olefin and the selectivity are best. Under the optimum reaction conditions, the conversion rate of olefin with Al-MCM-41 grafted by the ionic liquid catalyst is 95.32%.