The Shuibuya Dam is the highest concrete faced rockfill dam (the height is 233m) in the world. The dam site is located in Enshi Autonomous Prefecture, Hubei province, china. The reservoir level is a maximum of 400m. When the dam was partially completed, water impoundment was started. On May 10, 2007, when the reservoir level achieved at 289m, a landslide located on the bank of Modao-he River moved rapidly, a tributary of the Qingjiang River. 14 houses collapsed and moved into the river, but nobody was killed due to timely geological prediction. For the purposes of landslide disaster mitigation in the reservoir areas and identification of landslide movement and deformation caused by the change of reservoir level, some researches were conducted, such as geological exploration, some soil tests and numerical simulation and monitoring system. In this paper, the causes of landslides and slope failure mechanism and the stability of slope were simulated by using DDA method and FLAC3D for the different reservoir’s level.