This study is focused on the kinetic characteristics of photocatalytic degradation of gaseous organic compounds on modified titanium dioxide/activated carbon composite photocatalyst (MTA). The MTA, which co-doping with iron (Fe) and nitrogen (N), was synthesized by a sol-gel method, and its photocatalytic performance was investigated under different reaction conditions. The experimental data obtained were tested by the zero, first and second order kinetic model, and the factors affecting the kinetic model were analyzed. It was clearly demonstrated that the experimental data of toluene and acetone on MTA fit quite well with second order kinetic model equation, but the experimental data of formaldehyde fits well with zero order kinetic model equation.