Two landslides have occurred in Baige Village on October 11 and November 3, 2018, respectively, blocking the main flow of the Jinsha River and forming a barrier lake, causing a great economic damage. In order to better understand the cause of landslide formation and avoid the recurrence of such disasters, the Baige landslide in Jinsha River is taken as the research object to carry out the field investigation and the geological background analysis. The results show that the landslide is located in the Jinsha River suture zone between the Qiangtangterrane and the Songpan-Ganzi fold belt, and the Boluo-Muxie fault is developed at its rear edge. Simultaneously， the formation of Bogong Gully formed under this fault increases the seepage of groundwater in the study area.The main outcrops in the study area are the Triassic serpentinite and the Proterozoic male pine group gneiss and the borehole data show that the serpentine strata are strongly weathered and the rock masses are extremely broken， which provides favorable conditions for the occurrence of landslide groundwater that contributes the landslide. In addition, the serpentine strata combine with the gneiss that acts as a water-barrier layer in footwall to forming the water storage structure of intrusive contact zone and weathered crust. The slope of the Baige landslide is located on the concave bank of the Jinsha River, which is prone to toppling, bending and cracking deformation due to the strong erosion of the valley, the side erosion of the concave bank and the gravity of the landslide body. The water in Bogong Gully has been infiltrating into the landslide body for a long time, reducing the shear strength and effective stress of the soil, and gradually transforming the serpentine strata into a creep zone, which leads to the occurrence of Baige landslide under the trigger of the extreme rainfall event in 2018. It is pointed out that further risk management measures should include strengthening the depth of geological exploration and increasing the construction of drainage measures based on existing prevention and control.