A chemical kinetic model for determining the mole fractions of stable and intermediate species for CH4/NO2/O-2 flames is developed. The model involves 30 different species in 101 chemical elementary reactions. The mole fractions of the species are plotted as a function of the distance from the surface of the burner. The effects of the equivalence ratio on the concentrations of CO, CO2, N-2, NH2, OH, H2O, NO and NO2 for lean CH4/NO2/O-2 flames in the post flame zone at 50 Torr are obtained. The flames are flat, laminar, one dimensional and premixed. The calculated concentration profiles as a function of the equivalence ratio and distance from the surface of the burner are compared with the experimental data. The comparison indicates that the kinetics of the flames are reasonably described by the developed model. The mole fraction of N-2, NH2, OH, H2O, CO2 and CO increase while the mole fractions of NO and NO2 decrease by increasing the equivalence ratio for lean flames.