Abstract: In order to solve the problem of high exhaust gas temperature in W-shaped gas-fired radiant tubes, three kinds of structures were designed to improve the heat exchanger performance. Numerical simulation was carried out by using ANSYS FLUENT software. The performance parameters of heat exchangers with different structures were obtained, such as exhaust gas outlet temperature, preheated air temperature, pressure loss, heat flux in each surface, and heat resistance change with and without baffles. It is shown that the quantity of heat exchange increases by 57.6% after the central air tube changes from one tube of φ79 mm to six tubes of φ33 mm and by 20.7% through adding a double trip of exhaust gas. After inserting the sealed baffle and porous baffle, the quantity of heat exchange increases by 5.7% and 5.3% respectively, and the thermal resistance between air and exhaust gas decreases both by about 20%. The pressure loss of the porous baffle is lower by 47.4% than the sealed-baffle.