Cr, Ti-substituted TiO2-loaded MCM-41 (TiO2/Cr-Ti-MCM-41) catalysts were prepared, and their photocatalytic activities for decomposition of 4-nitrophenol (4-NP) in visible light were studied. The effect of H2O2 on the photocatalytic decomposition of 4-NP was investigated. Ti-substituted MCM-41 exhibited an absorption in UV range, and the incorporation of both Ti and Cr in the MCM-41 framework created visible light absorption. The visible light absorption capability of TiO2/Cr-Ti-MCM-41 increased with increasing TiO2 loading. The photocatalytic activity of CrTi-MCM-41 for degradation of 4-NP in visible light increased with increasing TiO2 loading up to 33 wt%. The addition of H2O2 enhanced the photocatalytic activity of 33 wt% TiO2/Cr-Ti-MCM-41 for decomposition of 4-NP in visible light. H2O2 was found to promote the adsorption of 4-NP on the Cr-Ti-MCM-41 surface, leading to increased reaction rate. In addition, H2O2 may act as an electron acceptor during photocatalytic reaction, thereby lowering the electron-hole recombination and increasing the efficiency of hole utilization.