A heat release analysis procedure was developed for a two-stroke spark ignition engine. The model was used to calculate instantaneous heat release rates, cumulative heat release and mass fraction burned of base engine and catalytic engine. The combustion chamber of the catalytic engine was coated with a catalyst material by plasma spraying method. The tests were conducted with different air-fuel ratios and heat release analysis was carried out for both base and catalyst coated engines. Engine cylinder pressure traces of 2000 continuous cycles were recorded using a pc based data acquisition system. The average of these traces was calculated and used as input to the heat release model. From the heat release rate various combustion characteristics, such as delay period, start of combustion, end of combustion and combustion duration were calculated for the base and catalytic engines. The results indicate that the heat release model could be used for the calculation of combustion parameters and accurate enough for the present purpose. The calculated combustion parameters indicate that the catalyst induces pre flame reactions of fuel air mixture before combustion, which reduces delay period and increases the combustion rate. The combustion duration of catalytic engine was reduced by 8 degrees at 0.8 equivalence ratio.