Abstract: The loess high-slope on western end of Shui Lian Dong colliery is an old landslide debris back-wall. There is an old landslide debris depost in the slope bottom. Surface water can infiltrate into the slope through loess uprightness joints and cranny. The groundwater flow gradually causes the formation of water cavities in the upper slope region. The slope further has loess stratification, obliquity (from 5to 10) and paleosols place. Surface water infiltrate into paleosol and induce water cavity exit with the top water cavity transfixion. The paleosol ideally prevents water. The loess stratification leans to ravine. The slope is unstable and will fail under the action of precipitations.