In this study, the numerical simulation of turbulence hydrogen-methane blending flame was performed by using the CFD code Fluent in a conical entry combustion chamber. The main aim of the presented study is to determine the best combustion model constant to be agree with experimental measurements in numerical simulation of the hydrogen-methane blending fuels. In the numerical simulation, the fuel including 30% hydrogen and 70% methane by volumetrically, 40 kW thermal power, and 20% of excess air was used. In addition, the fuel mixture of 30% hydrogen and 70% methane by volumetrically was also used to determine the effect of hydrogen amount on the emissions including NOx, CO ye CO(2) in the numerical simulation. Numerical simulations of the blended fuel, two different values (A=4 and A=1) of the combustion model constant A were used. In order to determine the most suitable combustion model constant, temperature, NOx, CO, and CO(2) measurement values were compared with numerical results. The velocity, temperature and gas composition distributions obtained from numerical simulation were also given and discussed in this paper. In numerical simulations of the hydrogen-methane blended fuel combustion, it is determined that the predictions for combustion model constant of 1 are closer to experimental values compared with the predictions for combustion model constant of 4.