The selective catalytic oxidation of toluene with hydrogen peroxide over V-Mo-based catalysts under mild conditions was studied. The promotion effect of Mo on the catalysts was studied with V/Al 2 O 3 and Mo/Al 2 O 3 as reference samples. The catalysts were characterized by XRD, TPR, and XPS techniques. The results show that the addition of Mo to V/Al 2 O 3 may change the distribution of V species on Al 2 O 3 surface. Over V-Mo/Al 2 O 3 catalyst, highly dispersed amorphous V species facilitates benzaldehyde formation, and crystalline V 2 O 5 species increases the conversion of toluene but decreases the selectivity to benzaldehyde, while AlVMoO 7 species favors both the conversion of toluene and the formation of cresols. The yield of benzaldehyde depends remarkably on the surface O/Al and Mo/V atomic ratios, and gets to a maximum value of 13.2% with a selectivity of 79.5% at an O/Al atomic ratio of 3.0 and Mo/V atomic ratio of 0.7.