Abstract: Although the k ε g turbulent combustion model becomes widespread in engineering application,but the coefficients of the model C R,C g1 ,C g2 and expressions of the square of concentration fluctuations g used by researchers are different.In fact,the effects of these coefficients and g expressions on reaction rate and temperature profiles are significant.This paper aims at providing optimal values of these coefficients and rational g expression.Numerical calculations were carried out for recirculating reacting flow behind a bluff body burner.It is shown that C R is given by C R=(ΔT /1000) 2g 1/2 /g 1/2 max ln (1+2g 1/2 max /g 1/2 ), C g1  is defined as C g1 =2/σ f, C g2  is 2 in this prediction. The prediction is in favourable agreement with the experimental measurements.