In order to study the effect of operating parameters on the heat release models calculation result of compressed natural gas (CNG) engine and confirm the models application conditions, Gatowski et al model, Apparent heat release model and R—W model were used to calculate heat release rate and mass fraction burned based on the cylinder pressure and crank angle data measured from a spark ignition CNG engine. The effect of engine operating parameters on the calculate results of different heat release models were discussed. The results show that the difference of heat release rate and mass fraction burned calculated between Apparent heat release model and R—W model is not obvious, which indicates that the two models can be in common use. The three models are affected slightly by ignition advance angle and excess air ratio. Difference among three models calculation results is not huge with small throttle opening. Compared with the other two models, the calculation results of Gatowski et al model are affected significantly by engine speed. The three models substitutes mutually under the condition of small throttle opening or high engine speed. Gatowski et al model is more accurate and suitable for slow engine speed compared with the other two models.