The invention relates to a diesel oil ignition 
natural gas engine 
combustion system and a control method thereof. The diesel oil ignition 
natural gas engine 
combustion system comprises an engine body,a diesel oil inlet 
system, a 
natural gas inlet system, a variable cross-section 
turbocharger VGT, an 
exhaust gas recirculation system EGR, a variable valve 
regulator VVT, a dual-fuel ECU, a comprehensive ECU, a computer and a power source, wherein the 
exhaust gas recirculation system EGR comprises an EGR 
intercooler and an EGR valve. According to the system, according to different operation conditions of an engine, accurate control over the 
fuel gas amount is achieved through strategies of adjusting a gas channel and gas injection of a gas injection valve in a cylinder, 
mixed gas with different filling amounts and layering states is formed in the cylinder, 
thermodynamic state control is coupled on the basis, through combined control of the variable valve 
regulator VVT and the exhaust gasrecirculation system EGR and cooperation of different equivalent ratios, stable ignition and controllable 
stratified combustion under various working conditions are achieved, the natural gas replacement ratio of a dual-fuel engine is further increased, and efficient and clean 
combustion within a wider working condition operation range is achieved.