In this paper, the performance of domestic gas burner heating unit is enhanced by optimizing secondary air of combustion that it is controlled by control of area entrance vent of secondary air and the heater second furnace vent. In order to determine the appropriate extent of the area of air suction vent, second furnace vent was closed by experimental methods and a valve with opening and closing capabilities was applied to the under part of the first furnace of the heater and the effect of closing this valve on increasing the heater efficiency was studied. The heating unit is first modeled as a three dimensional physical domain for flow of gases, and conservation equations of mass, momentum, energy, species and radiation are discretized over the meshing system of finite volume method provided in the domain. Experimental set-up to measure and validate the numerical results is equally established. Results show that by closing 84% of secondary air suction vent and complete closure of the second furnace vent, mass flow rate of air suction becomes 0.0035 kg/s. In this condition, a 9% increase in the mean heat transfer rate from furnace surface of the heater will occur