Two types of volatile organic chemicals (VOCs), acetaldehyde and o-xylene, were selected to probe the different adsorption and photodegradation mechanism of gaseous photocatalysis. Reduced graphene oxide (rGO)-TiO2 nanocomposites were prepared by facile solvothermal process to perform the photocatalytic reactions. In the experiments, the removal efficiencies of the acetaldehyde and o-xylene at 80 mLmin(-1) flow rate were only 15% and 12% when P25 was applied, while the efficiencies were sharply increased to 42% and 54% by using 0.5 wt% rGO-TiO2 as the photocatalyst, respectively. Interestingly, it is notable that the removal efficiency of o-xylene was higher than that of acetaldehyde with identical rGO-TiO2 photocatalyst. Experiments suggested that there were possibly two reasons. Firstly, the adsorbance of o-xylene was more than that of acetaldehyde owing to the at-at conjugation between rGO and aromatic compounds, which was proved by adsorption equilibrium and TPD tests. ESA tests proved that rGO can promote the generation of surface (OH)-O-center dot radicals and depress the O-center dot(2)- radicals formation. Compared with the dominant role played by O-center dot(2)- radicals in the degradation of acetaldehyde, an almost equal position of O-center dot(2)- and 'OH radicals was observed in the degradation of o-xylene according to the subsequent radical scavenger experiments. Moreover, the optimized rGO-TiO2 exhibited sustainable photocatalytic activity at 40-120 mLmin(-1) flow rate through 160 min tests, while P25 was deactivate only after 25 min. This work demonstrated the different adsorption and degradation characteristics of two types of VOCs, which could propel the target orientation design of photocatalyst in VOCs removal applications.