A large amount of what is produced by the fluid catalytic cracking unit in oil refineries is light cycle oil. Light cycle oil usually contains high levels of sulfur compounds, such as thiophene and dibenzothiophene. In this work, sulfur was removed by catalytic oxidative desulfurization. First, the mesoporous 5%Ni10%Mo/gamma-Al2O3 catalyst was prepared by the incipient wetness impregnation method. The prepared catalysts were characterized by X-ray diffraction, N-2 adsorption/desorption, inductively coupled plasma mass spectrometry, scanning electron microscopy, and NH3 temperature-programmed desorption. The catalytic activity was measured with catalytic oxidative desulfurization, and light cycle oil was used as feed, with 13000 ppm total sulfur. To reach the optimum condition for the oxidative desulfurization process, the effects of different oxidants, catalysts, time periods, and temperatures on the oxidative desulfurization process were investigated. The optimum condition for the oxidative desulfurization process was obtained at 1 g 5%Ni10%Mo/gamma-Al2O3 catalyst, 1 ml H2O2 as an oxidant, 30 degrees C, and 120 min. At this optimum condition, the total sulfur in light cycle oil was reduced from 13000 to 623 ppm.