Abstract: Large landslides and landslide group are characterized as large size, complicated formation mechanism, many inducing factors, serious damaging, difficult in harnessing and so on. Shagong Ancient Landslide by Sichuan-Tibet Highway is a typical loose accumulational landslide. This paper describes the geographic location, topography characteristics, features of geological environment and landslides in detail based on field survey data. Through the analysis on its motion characteristics, failure modes, it is determined that the ancient landslides are retrogressive one. The results showed that the coupling of fragile geological structure composed of moraine loose overburden and sandstone, the tectonic activity and water-rock interaction are the main causes of the formation, which is important for landslide treatment.