Flame characteristics configured flames can be strongly dominated by the combination of the burner and furnace. In this study, the effect of the flow field has been examined in terms of the emission of NO_x by LDV measurements furnace. The experiment was conducted in a variety of condition of the inner diameter of the cylindrical furnace,the global equivalence ratio and the turbulence at the flame boundary in the configuration of jet diffusion flames in cylindrical furnaces. As a result, it was found that increasing these parameter enhances recirculation of burned gas, and decreases the emission of NO_x.