50%。 A natural gas engine with a separate chamber and compound fuel supply system was designed based on stratification combustion theory. Simulation of ignition and combustion mechanism of the engine was carried out by coupling multidimensional computational fluid dynamic (CFD) code FIRE with detailed chemical kinetic mechanism. The results showed that it is possible to achieve stratification of mixture concentration and temperature in main chamber and by-chamber, and realize stratified combustion mode of compound fuel supply so as to have broaden operating range. The mean indicates pressure reached 0.63MPa and is 50% higher than mode of inlet fuel supply.