Abstract: A small experimental furnace was established,the hot simulation test for coherent jet heating cold metal material was conducted,the flame was measured,and the off gas composition was sampled and analyzed in different stages. The results show that the coherent jet flame presents the different characteristics in different stages,and the composition of combustion products is in change. Under the effect of cold metal material,little CO₂ appears,O₂ increases,and CO decreases; in the melting stage,O₂ rises and CO reduces gradually,and the mass fraction of CO₂ stays about from 1% to 2%; compared the decarburization stage with the melting stage, O₂ reduces,CO increases,and CO₂ increases little; in the decarburization stage,the carbon content in molten steel reduces gradually, CO₂ and O₂ rise a little,but the CO content reduces violently. Every composition in the coherent jet flame connects with each other,CO content increases as O₂ content reduces; in the melting stage,CO content increases as CO₂ content increases,but in the decarburization stage,CO content reduces as CO₂ content increases.