Abstract: Multi-stage intrusions of dikes can change the rock and slope structures greatly, and further change the deformation and failure mode and the stability of the slope. This paper examines the Gaxiapa slope in the dam area of the Lenggu waterpower station at the midstream of the Yalongjiang River as a case study. Before dike intrusions, Gaxiapa slope was a stable slope with thin-middle layer sandstone. The bedding dip direction is opposite to the slope dip direction. After intrusions, the slope constitutes interbedded sandstone and granite dike. The rock was cracked by crushing of the dikes. The original deformation mode bending-dumping changes into outburst of retaining wall.The comparatively intact sandstone in the middle became the retaining wall, which blocks the sliding of the cracked rock at the back, together with the front dike. However, the front dike is deforming severely and in a critical steady state now. If the front dike fails, the Gaxiapa slope is likely to slide down entirely. The result of the failure mode analysis is validated using 3DEC numerical simulation software. The conclusions of the study can be of some value for the similar study, and provide the theoretical support for the stability analysis and prevention of the landslide with the similar structures.