The technology of using high reactivity coke in iron-making process by blast furnace has been verified to promote the reduction of iron ore in the thermal reserve zone through theoretical analysis combined with experimental research. However, the absence of relative calculation model makes it difficult to determine the coke saving ability quantitatively and supply substantial guidance for industry. In present study, thermal reserve zone and high temperature zone are taken as investigation objects and a calculation model has been established to study the influences of high reactivity coke on reduction of iron oxide, shaft efficiency, and fuel rate. Combined with calculation model, the industrial practice is analyzed by concluding a new important index namely the proportion of high reactivity coke taking Boudouard reaction in the blast furnace (PCTBR for short). The results show that, introduction of high reactivity coke could reduce the temperature of the thermal reserve zone and promote the exothermic indirect reduction of FeO. The high reactivity coke reduces direct reduction, and decreases the heat consumption of high temperature zone by allocating the direct reduction region reasonably as well, which leads to a lower fuel rate. The fuel rate has been reduced by 16.84 kg tHM−1 when the high reactivity coke amount participating Boudouard reaction is 40 kg tHM−1. The PCTBR of WuJing coke and Ca-rich coke is around 7.8%.