Abstract: Heat exchangers are the main equipment of hot-blast stoves. Heat exchange area of the cylinder radiation exchanger has computed by LMTD when air has heated to different temperature. Draw the graph of relation of temperature differenceΔt=t2-t1and average heat exchange area (F/(t2-t1)). The concept of the economical temperature district is proposed on the basis of it. It has the more practical value in the choosing and designing the exchangers of the hot-blast stoves with high-power and high temperature.