The research is for the firs floods and the post-drought in Yunnan area in 2010. The strong rainfall and the hole pressure change are the red rock landslide most essential factor, so an apex post-modulus which indicates the effect of pore-water pressure on stress—strain curves transition is defined at the first. By combining with the stiffness criterion of landslide is analyzed. Consequently rainfall and other conditions changes have important effects induced landslides. It union research thinks of the elephant mountain landslide area, that red rock landslide slope body displacement and the rainfall amount relations and the slope body full water area compares and the stability of slope coefficient relations, establishes one under the strong rainfall function the red rock landslide cusp sudden change model, the quota and qualitative reveals the strong rainfall to the red rock landslide trigger action. This developed model may carry out some use full knowledge to understand the disaster mechanism and the evolutional or accumulative process of hazard factors in mountain red layer of the slope stability problem, which may mean the further to advance the technique of forecasting, it can provide important reference to the disaster prevention.