Abstract: With regard to an ancient bank landslide near a dam, centrifugal model tests on instability mechanism under reservoir impoun dment and rapid drawdown are carried out. The slope models are constructed with the consideration of large-size and heterogeneous characters of the prototype . The centrifuge tests are accompanied with real-time control of water levels, and followed by laboratorial test for physical status and strength of model slope soil. The results of centrifugal tests show that the rising water level in the reservoir leads to decreasing slope foot sliding resistance, as well as leads to edge cracks and slump. Also, the results reveal that the rapid drawdown causes slope body to produce outward hydrodynamic pressure, aggravates slope foot sliding and creates pull-typed landslide trends. When the slope foot is reinforced, the deformation is controlled and stability is improved. The soil tests of model slopes, before and after centrifuge tests, indicate that the slope foot sliding will lead to the redistribution of soil density and moisture, at the same time lead to the strength reduction near slide zone. Moreover, the cohesion of immersed soils will reduce until it vanishes finally.