In the process of oil pipelines’starting to convey, precise calculation and prediction of temperature field of the soil around pipelines and law of medium temperature in the pipelines changing with time are the key to identify the time of putting oil in and preheat medium totals. By water as preheat medium, and calculations of conducting heat’s numbers in the process of pipelines’ preheat under different flowing speed circumstances, it analyzed distributions of temperature field of the soil around preheat pipelines and temperature dropping along pipelines with distances, and finally get oil pipelines’ preheat conditions under flowing speed of various medium, which can help set corresponding oil-conveyed technique and attain the goal of safety and saving energy.