Abstract: Slope excavation and rainfall infiltration are often important factors affected slope stability.In this paper,the rebuilding of HuNan national highway is studied.Based on monitoring data and numerical analysis,the process of slope deformation is studied during the slope cutting and under rainfall conditions.The results show that the slope failure is a gradual process.Different factors can influence the slope stability and have different functions in the process.Slope excavation is the inciting factor which can lead to the failure of shallow slope body.For the slope is excavated,the stress balance of the slope body is destroyed.Slope body has a redistributed stress state.Then the shallow sliding surface is formed.The rainfall infiltration is the inciting factor leading to the deep sliding surface.The rainfall infiltrates the slope body along cracks.Deformation difference can increase on the both sides of shallow sliding surface.Then the pull-type landslide can be emerged.The high porewater pressure is in the interface between debris and strong weathered shale.The sliding zone is generated under the action of water-soil gradually.Consequently the deep sliding surface is emerged.