The present invention provides a catalyst composition for inhibiting the inactivation of a catalyst for purification of compressed natural gas combustion system exhaust gas on which a noble metal component comprising platinum and palladium is supported. An oxidation catalyst, for a compressed natural gas vehicle or static combustion system exhaust gas, in which a first alumina impregnated with platinum, a second alumina impregnated with palladium, and a ceria component are supported on a ceramic support, has a barium cocatalyst supported on the first alumina, thereby greatly inhibiting inactivation of a CNG lean burn engine catalyst.