Abstract: The theoretical flame temperature before the tuyere in a blast furnace(BF) is one of the important parameters to measure the thermal state of the hearth.However,it is ignored that SiO₂ reduction before the tuyere can impact the theoretical flame temperature.The coke temperature entered the raceway and the SiO₂ content at different locations before the tuyere in the BF were obtained by studying tuyere-level samples from the BF.And then the reduction rate of SiO₂ before the tuyere was determined and the theoretical flame temperature formula with regard to the effect of SiO₂ reduction was established.Finally,under the condition of pulverized coal injection(PCI) and oxygen enrichment,the effect of changing the ash content in coal on the theoretical flame temperature was analyzed and discussed.