The catalytic oxidation of ethylene to carbon dioxide in excess air has been studied atsteady state.The catalyst temperature was measured for various feed temperature and concentration.The bifurcation diagrams Which describe the dependence of the catalyst temperature on the feed gastemperature were obtained for different ethylene concentrations in the feed gas.The ignition and ex-tinction temperatures were found out and the unique and multiple steady state regions could bedetermined from these diagrams.The experimental results can be satisfactorily explained by thecatastrophe theory and singularity theory.According to the steady state multiplicity features an at-tempt to discriminate the competitive kinetic models was made for the reaction. The catalytic oxidation of ethylene to carbon dioxide in excess air has been studied at steady state. The catalyst temperature was measured for various feed temperatures and concentration. Bifurcation diagrams Which describe the dependence of the catalyst temperature on the feed gastemperature were obtained for different ethylene concentrations in the feed gas. The ignition and ex-tinction temperatures were found out and the unique and multiple steady state regions could be determined from these diagrams. The experimental results can be satisfactorily explained by the catastrophe theory and singularity theory. According to the steady state multiplicity features an at-tempt to discriminate the competitive kinetic models was made for the reaction.