Aimed at the difficulty of starting up and knocking on the homogeneous charge compression ignition natural gas engine, a hot surface assisted ignition system with stratified charge was developed and it’s operating characteristics was investigated. Results from experiments showed that engine starting up is easy with natural gas low pressure supply method. It is advantageous for the mixture concentration stratification forming with decreasing passage size, increasing high pressure injection ratio and decreasing advanced angle of high pressure injection. At a result, the interval angle of ignition between main and auxiliary chamber was increased, the pressure raising ratio and the heat release ratio around the top dead center were retarded obviously, so knocking was restrained. With passage diameter between the main and auxiliary chamber at 8 mm, the maximum power is 83% of the original engine at 1200r/min and 73% of the original engine at 1400r/min respectively, Meanwhile NOx emission has been reduced compared to the direct injection natural gas engine. 