Abstract: Preheating process during commissioning of buried hot oil pipelline is a process of unsteady heat transfer, and soil temperature field in the process of oil transportation involves in 3D unsteady heat transfer for oil flowed along the transverse section (radial section and tangential section) of pipeline.Simplified treatment on the mathematical model of positive preheating process for buried hot oil pipeline is made and model's solution is carried out with numerical calculation method; curve charts of preheating temperature variation with transportation distance are drawn for some oil pipeline.Calculation and analysis on relevent heat storage capacity of soil during positive preheating are made, and different outlet temperatures do not influence the time for heat storage capacity to achieve at stability, but they will result in different absolute values for heat storage capacity.