Abstract: Effective operation of Xiaolangdi multipurpose project is greatly affected by the landslide No.1 on account of poor stability and gigantic volume of the landslide. So its stability and deformation monitor is extremely important. The paper studies the deformation characteristics and forming analysis of the landslide No.1. The qualitative analysis and quantative estimation are introduced. The analysis and estimation of the landslide provides analysis basis for the deformation monitor.