A dynamic evaluation of landslide sliding surface strength parameters approach is proposed to analyses the stability of large-scale landslides which are controlled by groundwater fluctuations within the slide. The proposed approach utilizes a dynamic model in conjunction with stress state to describe the strength parameters of the sliding surface. Both experimental and theoretical analyses are carried out. Subsequently, three-dimensional numerical modelling of the landslide is carried out to explore the influence of three-dimensional sliding surface geometry and groundwater level fluctuations on sliding surface strength parameters. Simulations of the slide suggest that the approach proposed can describe the strength parameters of Badi landslide. In addition, simulations indicate that groundwater has not significantly influenced on sliding surface strength parameters under situ stress state.