Abstract: The filled soil of Shenzhen landslide is treated as saturated porous media. The excess pore pressure due to fast filling process is derived using the classical one-dimensional consolidation theory by assuming the thickness of the filled soil to increase linearly. Meanwhile, another part of the excess pore pressure induced by the soil contraction under shear deformation is derived by using the modified Cam-clay model. Then the effective stress is obtained by subtracting the pore pressure, i.e., the static pore pressure and the two parts of the excess pore pressure, from the total stress. The undrained shear strength can be expressed by the effective friction angle and the effective stress. Finally, the landslide is simulated using the material point method by assuming an undrained run-out process in which the soil strength keeps constant. The destructive effect of the sliding soil on the buildings is also analyzed. The proposed theory can be used to explain the extraordinary flow ability of the soil satisfactorily.