We theoretically investigated the relationship between the activity of the supported Pt catalyst and the oxide support type. The activation energies (E-a) of the propylene (C3H6) oxidation reaction with Pt catalysts using different oxide supports were estimated by an Arrhenius plot. The minimum and maximum E-a values were 99 kJ/mol for Pt/TiO2 and 121 kJ/mol for Pt/La2O3, respectively. The chemical potentials of the oxide support (mu(MOx)) were estimated by the density functional theory (DFT) calculations. The calculation results showed that the mu(MOx) values varied depending on the thickness of the oxide support, but they were not strongly dependent on the crystal structure of the oxide. It was found that E-a can be expressed by the quadratic equation of mu(MOx), and Ea assumes the minimum value when mu(MOx) is close to the chemical potential of the O-2 molecule (approx. -6 eV). We succeeded in expressing Ea as a quadratic expression of mu(MOx) by theoretical consideration using the Bronsted-Evans-Polanyi (BEP) principle and the hard-soft-acid-base (HSAB) concept, i.e., the Ea value for the C3H6 oxidation reaction depends on the binding energy of the catalyst and oxygen. It was also determined that the mu(MOx) value is one of the descriptors affecting the activity of the supported Pt catalyst.