The intake, compression and combustion process of the shallow bowl and swirl chamber spark-ignition natural gas engine was simulated to study the effect of the chamber structure on combustion of the natural gas engine. The combustion duration, gas flow in the cylinder during the combustion process and position of the flame front surface was given. The experimental contrast analysis of the two kinds of combustion chambers was also provided. The simulation and experimental results showed that the restriction effect of the spit hole on the swirl chamber could improve the heat transfer and mass transport model between the gas burned and unburned, which could increase the flame propagation rate.