A visible light active photodegration catalyst was prepared by doping MoO3 into MgF2 matrix. The addition of SO42- into MoOx/MgF2 could improve the catalytic activity greatly and an acetone conversion of 96.1% under visible light was obtained on the SO42-/5% MoOx/MgF2 (SMM) catalyst. By BET, XRD, Raman, FT-IR, XPS, UV-vis technology the specific area, structure and photoadsorption ability of the catalysts were characterized. The high photocatlaytic activity of the SMM catalyst is attributed to its large specific area, the high dispersal of MoO3 domains in MgF2 and the inhibiting effect of MgF2 matrix on the electron-hole pair recombination. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.