Abstract: Based on the observation data of vertical and horizontal deformation, this paper analyses the characteristics of surface deformation in the area before and after the retaining of water and points out that though the time duration after retaining of water is not long, yet surface deformation can be clearly observed. It shows that the reservoir area tends to subside and the displacement vector is directed toward the reservoir area. The data might be helpful in studying and estimating the trend of induced earth-quakes in reservoir area,