In order to improve the efficiency of steam transmission and reduce the loss of pipe network, the overhead pipelines of 1 438 m DN 250 and 403 m DN 150 in the industrial park were reconstructed by a new composite insulation technology. The implementation effect was analyzed through field test and theoretical analysis. The results show that the temperature differences between the ambient temperature and the average temperature of the surface of DN 250 and DN 150 steam pipelines decrease by 10.8 ℃and 8.3 ℃ respectively after thermal insulation reconstruction. The heat loss of DN 250 steam pipe is reduced from 177.9 W/m2 to 52.3 W/m2, and that of DN 150 steam pipe is reduced from 131.4 W/m2 to 34.9 W/m2.