Abstract: The purpose of landslide monitoring is to obtain the characteristics and evolutionary process of landslides.For some important sites,monitoring in deep ground is the most direct and effective means to determine whether or not potential landslide exists,in this paper,five boreholes for underground monitoring are set on two profiles of a slope behind a hydropower plant.Slide area,slope activity,sliding direction,sliding surface and types of the landslide are discussed and analyzed.The monitoring results reveal that it is a retrogressive landslide with obvious activity.The displacement velocity of the landslide is large and it has accelerated in the rainy seasons.Sliding surface in the slope front has been locally penetrated.It alsohas creep deformation in the upslope.