In a constant volume combustion chamber, a study of investigating for relationship between NOx emissions and a non-homogeneity distribution of methane-air mixture was conducted Non-homogeneity distribution was generated by varying a period after fuel injection and movement of perforated plate. Non-homogeneity distribution was measured by the acetone planar LIF technique and the heterogeneity index was defined. Initial pressure and temperature in the chamber was changed The effect of NOx and combustion efficiency on the heterogeneity index and the initial condition in the chamber was studied in detail. The trend of NOx and combustion efficiency was varied in different heterogeneity mixture at the same air fuel ratio.