A heat release analysis model was developed for a two stroke spark ignition engine. The model was used to calculate the instantaneous heat release rates, mass fraction burned and temperature of the burnt and unburned mixture of the base engine and catalytic coated engine. The combustion chamber of the catalytic engine was coated with catalyst material like chromium by plasma spraying method. The experiments were conducted with various air-fuel ratios and heat release analysis was carried out for both base and catalytic coated engine. Engine cylinder pressure traces of 2000 continuous cycles were recorded using pc based data acquisition system. The average of these traces were calculated and used as input to the heat release model. The heat release rate from the single zone model was used to calculate combustion duration, start and end of combustion and burnt and unburned temperature from the two zone combustion model for the base and catalytic coated engine. 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 catalyst engine was reduced by 8 degrees.