Along long transmission pipeline, geology and hydrology is different, the difference of buried pipeline depth is great. The corresponding natural ground temperature and pipelines-temperature field are also different. If the average or equivalent depth is considered only, the pipeline computation will make a very big error. The use of numerical method will consider the fact that the numerical model approaches the actual frozen earth geological condition and the nonlinear characters, which appears especially important. The limited unit method was used to calculate the soil temperature field around the pipelines by three dimensional numerical compute under the different buried depth conditions. The result indicates that the pipeline temperature change is, to some extent, affected by the buried depth, especially in the frozen earth area, the temperature difference between natural soil and pipelines' surroundings is greater.