Abstract: Mg/Ce-SBA-15 mesoporous molecular sieves were synthesized by using Ce-SBA-15 as support and magnesium nitrate as precursor through impregnation method. The samples were characterized by XRD, N₂ adsorption-desorption, BET, SEM, NH₃-TPD, Py-FTIR and TG-DTA techniques. The results indicate that the original crystal structures of SBA-15 remain unchanged after modification with Mg, but the number of weak acids were increased especially L acids. The performances of catalysts in phenol alkylation with methanol were studied in a fixed bed reactor. The results showed that the catalyst showed the highest catalytic activity under the conditions of Mg content=7%, calcination temperature=550℃ and calcination time=4.5 h.At 460℃, n(phenol):n(methanol)=1:4, WHSV=3.0 h^-1 and atmospheric pressure, the conversion of phenol was 80.1% and the selectivity to o-cresol was 86.4%.