In the aim of investigating the deformation and failure modes of water-involved accumulation slope,physical model test on accumulation slope was conducted under the action of reservoir water level fluctuation.A model test platform with the base plate adjustable was designed and manufactured independently. And the basic mechanical properties of soil samples collected from Three Gorges Reservoir were determined. Results show that slope gradient has significant influence on the characteristics of slope deformation and failure: large-scale bank collapse occurrs during the rise of water level when slope gradient is large (50° and 60°), and the deformation failure mode is water level raising→denudation and tunneling↔ bank collapse→sinking platform→integral sliding→metastable state; whereas when the slope gradient is 40°, large sliding failure occurs during the water level drawdown, and the corresponding deformation failure mode is water level raising→slope settlement→ crack penetration→drop of water level→propagation of crack penetration↔ formation of slip surface→global slip; when the slope gradient is small (35°), there is no obvious deformation and failure in many times of water level fluctuation cycle.