The support effect on the low temperature propane combustion over supported platinum catalyst was studied by using a series of metal oxides as support materials: MgO, La2O3, ZrO2, Al2O3, SiO2, SiO2-Al2O3, and SO42--ZrO2. The catalytic activity varied with the support materials, and the platinum supported on more acidic support material showed higher activity. The support effect on the oxidation state of platinum was investigated by Pt L-II- and L-III-edge XANES. In the oxidizing atmosphere, platinum on the acidic support materials was less oxidized than that on the basic one, indicating that the oxidation-resistance of platinum is enhanced with the increase in the acid strength of support materials. This support effect in the oxidizing atmosphere is entirely different from that in the reducing atmosphere; the electron-deficiency of platinum increases with the increase in the acid strength of support materials under the reducing atmosphere. The relation between the catalytic activity and the oxidation state of platinum clearly indicates that the variation of the catalytic activity with the support materials come from the variation of the oxidation state of platinum, and that support materials affect the catalytic activity through the control of the oxidation state of platinum. These results suggest that the acid strength of support materials is an important factor for the design of the active supported platinum catalyst for the reaction under the oxidizing atmosphere.