Based on the heat loss occurred when a pipeline to transport hightemperature steam vapor overhead, it is established physical and mathematical models of steam pipeline,and compared to the three commonly used insulation materials of overhead pipeline. Research results showed that the application results of nano airgel composite reflective insulation was the best. The different steam temperatures of the temperature field of pipeline and insulation layer in, different diameter and different insulation thickness distribution were simulated. By analyzing the temperature field indicated that changing the diameter effected the heat loss of overhead vapor line greatly. When the diameter changed from 126 mm to 132 mm unit length, the heat loss increased 10.702 62 kJ/(h •m).