In this paper, a novel composite photocatalyst AgI/AgCl/TiO2 was prepared by ion exchange method and characterized by XRD, SEM and UV-Vis spectrometry. The as-prepared AgI/AgCl/TiO2 composites show much higher photocatalytic activity than AgCl/TiO2 and AgI/TiO2 under visible-light irradiation (lambda > 400 nm) in the process of methyl orange (MO) degradation. When the molar percentage of AgI to initial AgCl is 20% (sample SE-20%), the maximal degradation efficiency of MO has reached 85.8% after irradiation for 120 min. The enhancement of photocatalytic activity of the composite photocatalyst AgI/AgCl/TiO2 will be attributed to its good absorption in the visible-light region, especially low recombination rate of the electron-hole pairs based on the photoluminescence (PL) spectra investigation of AgI/AgCl/TiO2 and the matching band structures of AgI, AgCl and TiO2. The detection of reactive species by radical scavengers displays that center dot O2--and H2O2 are the main reactive species for the degradation of MO under visible-light irradiation. Moreover, PL analysis by using terephthalic acid (TA) as a probe molecule further reveals that center dot OH can be negligible for the degradation of MO. (C) 2011 Elsevier B.V. All rights reserved.