Caves and fractures are the main oil space in a fractured-vuggy carbonate reservoir which has strong heterogeneity.In order to research the characteristics of the oil-water interface during bottom water flooding, a 3-D visual fractured-vuggy reservoir model was designed and built on the basis of the S48 fractured-vuggy unit in the Tahe oil field. Using this model, bottom water flooding experiments were conducted, which led to the analysis of the fracture-vuggy unit oil-water interface char-acteristics, fracture-vuggy connections, oil-water interface characteristics, bottom water coning oil-water interface characteristics and filler’s influence on oil-water interface characteristics. The experiment results show that: in certain fractured-vuggy units, macroscopic oil-water interface height differences lead to stronger non-uniform flow distribution. When bottom water flowed vertically into a cave, the actual water bump height was higher than the height of the stationary state which was only affected by interfacial tension and gravity. We define this phenomenon as the "spring effect". In fractured-vuggy connections, the oil-water interface height in fractures was different from that in caves, the height difference was influenced by wettability, additional pressure on curved surfaces and connections of fractures and caves. Oil-water interface dimensionless height difference and oil recovery in fractures were negatively correlated. The oil-water interface in blind caves was convex, the bottom water lifts both the oil-water interface height and the convex surface height. The characteristics of oil-water interface were different when bottom water coning happened from wells in caves or fractures. What is more, fillers made a great influence on oil-water interfaces. This appeared as seepage characteristics in filling areas, the oil-water interface in the region of the filling lifting fast and forming water channels easily. There was no same oil-water interface in part. The result of experiments provides a theoretical basis for bottom water flooding and enhanced oil recovery in fractured-vuggy carbonate reservoirs.