A chemiluminescence (CL) instrument was developed to understand the CL behavior of catalytic oxidation of CO and hydrocarbons, which are major processes occurring in catalytic converters. The instrument is based on the cooperation among a gas mixer, a custom-made CL analyzer, and an on-line gas chromatography. The concept of the CL method was formulated by thoroughly investigating the CL emission during the catalytic oxidation of CO and C3H6 in the presence of O2 and/or NO under both stoichiometric and non-stoichiometric conditions. All the oxidation reactions were found to be CL-active, where the CL intensity increased exponentially with the temperature. The steady-state measurements showed good linearity between the CL intensity and the reaction rates, demonstrating that the CL emission is a direct product of the reactions. It was also found that the CL intensity per CO2 production was different among the reactions, most plausibly due to both/either the presence of multiple CL processes and/or the difference in the heat of the reactions. Based on the linear correlation between the CL intensity and the reaction rate, a feasibility study was successfully demonstrated for rapid catalyst evaluation in C3H6 oxidation.