Abstract: Taking the heat conducting oil used in Zhongmu——Luoyang oil pipeline as an example, theproblem on service life of heat conducting oil of heat medium heater is studied. The result shows that the high temperature operation, local superheating, nitrogen isolation free, and high impurity shorten the service life of heat conducting oil. In the light of the problems, some countermeasures against the problems, such as adopting by-pass dilatetion tank process, installing a cooling tank to isolate air, and heat conducting oil filtering and refinement, are put forward. Taking 3 or 4 years as a service period into account, expanding a service period of heat conducting oil could save a cost up to 100 ×10⁴ yuan.