The adsorption of volatile organic compounds (VOCs) and O2 on the surface of the catalyst was one of the vital progresses in the plasma-catalytic oxidation of VOCs. In this work the breakthrough curves of toluene adsorption on the 3%FeOx/SBA-15 were measured under the various O2 concentrations. The results showed that the breakthrough time of toluene reduced with increasing O2. Competitive adsorption was observed on the catalyst surface between O2 and toluene. The catalysts adsorbed the toluene under the various O2 concentrations were characterized by O2 temperature-programmed desorption (O2-TPD), and X-ray photoelectron spectroscopy (XPS). The desorption amounts of O2– and the Fe percentage on the catalyst surface were dependent on the O2 concentration during toluene adsorption. The experimental results of pure SBA-15 and 5%MnOx/SBA-15 indicated the competitive adsorption site of O2 and toluene was FeOx. In situ FTIR data of toluene adsorption on the catalyst surface indicated that the adsorption state of toluene could not be impacted by the competitive adsorption of O2, and the O2 adsorbed on the catalyst could oxidize toluene.