The mixed injection of CO₂ and O₂ in blast furnace is a novel method. The effect of alkali metal vapor on coke structure was studied by gas phase adsorption method. XRD, Raman and other characterization methods showed that K/Na metal vapor reacted with carbon matrix to form new minerals, which destroyed the original dense aromatic ring structure of metallurgical coke and reduced the high-temperature properties of metallurgical coke. In this work, the influence mechanism of alkali metals on coke in blast furnace in CO₂–O₂–N₂ mixed atmosphere was studied by thermogravimetric analysis. The dynamic analysis results show that when the heating rate is 5 K min⁻¹, the deviation value of VM is only 0.64%, and the corresponding urcm is 1.4%. Other experimental results show similar results, indicating that the product model (VM) has the best simulation effect on the reaction process of metallurgical coke.