Abstract: Taking the commissioning of Changqing Oilfield-Huhehaote Petrochemical Company Crude Oil Pipeline Project (Chang-Hu Crude oil pipeline) as an example, this paper describes the set-up method of temporary water delivery facilities in the commissioning of hot oil pipeline and gives the calculation method of the diameter of temporary water pipeline.Based on the related process, equipment parameters and the volume of water used during commissioning stored in the tank of reserve storehouse during the commissioning period of Chang-Hu Crude Oil Pipeline, related process parameters at the inlet of oil pump were calculated and then the best diameter was determined. The main factors influencing the volume of preheating medium include the distance between stations and the requirements on temperature field inleting the heating station, which determine the length of flushing section and the volume of preheating medium. The experience can provide areference to the commissioning of other hot oil pipelines.