The thermal efficiency of gas radiation tube is an important technical performance index of the radiant tube, for example in the references for the object, assuming air preheating temperature is 300 ℃ before modification, and modification after the air preheat temperature to 850 ℃, adopt the excess air coefficient of 1.02, before and after the modification by calculation, gas-fired radiant tube heating device before modification of only 62.21%, thermal efficiency and modified thermal efficiency is 85.30%, thermal efficiency is improved by 23.09%.High temperature air combustion than normal temperature required for ordinary air combustion excess air coefficient is usually smaller, such as using high temperature air combustion excess air coefficient of only 1.02, and use the normal temperature normal air combustion may need excess air coefficient of 1.1 or higher.If the temperature is higher, and considering the influence of excess air coefficient of thermal efficiency, thermal efficiency before and after the transformation will be greater with the increase of amplitude.