Abstract: Conditional moment closure(CMC) model proposed by Bilger is used for simulation of CH ₄-Air diffusion combustion and its NO _x formation,taking into account a radiant heat losses in this paper.Simulation is carried out by using k-ε-f-g model for velocity and mixed fractions,and a parabolic equation of conditional moment closure (CMC) for component concentration.A comparison of the prediction and experimental data demonstrates that CMC has good performance in the prediction of the fields of velocity,temperature and main component(CH ₄,CO ₂) concentration,the prediction of NO concentration is in agreement with in experimental data with acceptable departure.