The main goal of this paper is reducing emissions of nitrogen oxides and soot in the combustion chamber by injecting water in theintake air through a chamber (relative humidity). In this regard, an axially symmetric turbulent combustion chamber with fuel gas (methane) and non-premixed, derived from laboratory studies [9], has been considered. The other two-equation model of turbulence k-Ɛ, in both standard and realizable and to calculate the rate of reaction of combustion the Eddy Dissipation model (EDM) and the probability density function (PDF) were applied. The results of modeling showed that the most accurate model for turbulent flow, k-Ɛ realizable and for combustion, PDF. To reduce emissions, the relative humidity of the intake air in six different values ​​from zero to 100 percent have been examined. Results showed that by increasing the relative humidity, considered mildly reduced inlet air temperature and the resulting sharp decline in pollutants such as nitrogen oxides and soot seen compartment. while this value to NO and soot are respectively 5/67 and 8/71 percent. Failure to reduce thermal efficiency and a drastic reduction of NO and soot, showing the effectiveness of this method is to reduce emissions.