Abstract: The Baishi landslide is located at the west of Beichuan county, Mianyang, Sichuan Province. The landslide was detected due to fast deformation that caused several small collapses and falls in the front of the unstable slope as well as densely distributed tensile cracks in the slope. In order to better understand the stability status and estimate the failure time of the unstable slope, a comprehensive monitoring system was carried out after the deformation was reported. The monitoring was continued till the slope failed. This study analyzes the landslide deformation phases and failure mechanism using the monitoring data. The result shows that the failure mode of the Baishi landslide is bending-tensile(toppling).The failure has both the retrogressive and advancing features. The landslide is divided into several zones according to the spatial variation of deformation characteristics over the slope. The monitoring results indicate that the front part of the slope(Zone I-3)plays a key role in controlling landslide stability. Therefore, the monitoring data of this zone is significantly important for predicting the failure time of the whole landslide.