Abstract: Numerical simulation on non-steady state heat transfer law of oil product pipeline and crude pipeline laid in one ditch is carried out by adopting finite volume method. Influence of laying in one ditch and non-laying in one ditch on heat transfer law of buried pipeline is compared and analyzed, and influence of fluctuating parameters in surface temperature on heat flux and soil temperature for the pipelines laid in one ditch is calculated and analyzed. The research shows that laying in one ditch technology can improve soil temperature distribution around pipelines and decrease overall heat transfer loss of crude oil pipeline to the outside; increase of fluctuating amplitude of surface temperature and fluctuating period will intensify the amplitude value of heat flux at pipe wall, and it is harmful for smooth transportation of the buried pipeline, which should be improved by insulating measures.