This paper presents the preparation and characterization of TiO2/MCM-41 catalysts with different amounts of TiO2 loading or calcination at various temperatures. The activities of the samples were investigated under UV, ozone and UV-zone by the comparison of acetaldehyde degradation. The results showed that the application of photocatalytic ozonation (UV-ozone) produced the highest efficiency for acetaldehyde removal, indicating that a synergistic effect occurred when photocatalysis and ozonation are carried out simultaneously. The synergistic catalytic performance depended significantly on the composition of catalysts used. The TiO2/MCM-41 catalysts were superior to single TiO2 and MCM-41 with respect to the ozone-assisted photocatalytic oxidation of gaseous acetaldehyde, and the activity of the catalyst TiO2/MCM-41, with TiO2:MCM-41 = 5:10, is the highest one among these prepared catalysts. The improvement was attributed to the synergetic effect between adsorption, ozonation and catalytic reaction.