Abstract: The catalytic activity of MCM-41 and Fe loaded MCM-41 (Fe/MCM-41) for ozonation of p-chlorobenzoic acid (p-CBA) in aqueous solution was investigated. MCM-41 and Fe/MCM-41 were synthesized by a direct hydrothermal method and characterized by XRD, DR UV-Vis and FT-IR. The results showed that MCM-41 and Fe/MCM-41 presented mesoporous hexagonal structure with large surface area. The presence of MCM-41 and Fe/MCM-41 improved the p-CBA and TOC removal in the ozonation process, while Fe/MCM-41 showed better catalytic activity because of its synergistic effect with O3. The TOC (p-CBA) removal efficiency in Fe/MCM-41/O3 process was 51.4% (86.6%) at 60 (30) min, 39.4 % (79.4%) using MCM-41 as catalyst, only 35.4% (72.1%) with ozone alone.