Abstract: An anisotropic elastic visco-plastic constitutive model for structured soils was suggested.A new analytical model for describing the progressive slow movement of natural slopes was proposed,based on the relationship between velocity and visco-plastic strain rate.The destructuration of natural soil and suction were taken into account in the model.The analytical model could be used to investigate the influence of anisotropy,viscosity,degree of destructuration and fissure on the slope deformation.On the basis of progressive deformation and structure damage theory,the progressive deformation and failure of natural fissured soil and the field behavior of a natural slope were predicted using this model combrned with the observed data.