Abstract: In the light of water deposition in low-lying pipe section of oil product pipeline, which will make the pipeline corroded, mechanism to dewater with oil stream are researched and discussed. Taking a fixed dip round pipe section as a research objective, adopting momentum conservation and momentum integration relationship, including empirical relationship of interface shear stress, carry-over function of upstream oil stream on water deposition in inclined pipeline is analyzed supposing that the upstream oilstream is flowing at mean flow rate. Results show that when pipeline is at horizontal location with little water volume, water deposition within the pipeline can be carried off by upstream oil stream; if the dip of pipeline is enlarged or water volume is increased, the water volume will not be carried off，even countercurrent will produce. If using nonsteady flow model is considered, water deposition carry-off by oil stream can be effectively settled for oil product pipelines.