Abstract: Water deposit in oil pipeline causes severe internal corrosion. Room experimental loop with high-speed camera is built to study the motion state of water in low-lying and upward pipeline section. The effects of the water volume and the oil flow rate are analyzed. Results show that the water appears different flow patterns in different pipeline sections, which is different from that of the traditional two-phase flow. Because the density differences exist between water and oil, the water can attain to a dynamic equilibrium under the influence of the oil and the gravity and it is hard to be drained away in the upward pipeline. Based on the experiment, further study will be focused on the way to drain off the water to reduce the corrosion of the inner wall of pipeline.