The circulation and accumulation of harmful elements in the blast furnace leads to a decrease in gas utilisation and an increase in heat consumption, which can cause the increase of coke ratio. In this paper, the effect of harmful elements on the coke ratio was quantitatively studied using the Rist diagram. The results show that the effect degree of each harmful element on the coke ratio varies. The influence orders of accumulation times and loads of harmful elements on the coke ratio are Na > K>Zn and Zn > Na > K, respectively. The increase of heat consumption has more effect on the coke ratio than the decrease of gas utilisation. The total increase of coke ratio by the effect of K, Na and Zn is 14.2, 35.8 and 9.3 kg/tHM, respectively, of which the effect of heat consumption accounts for 55.9, 60.9, 60.9%, respectively.