Rainfall is an important factor to induce landslide instability, based on the theory of saturated - unsaturated and slope stability analysis, based on the same amount of rainfall and rainfall time, the Geo - studio software simulation tree landslide under different water level and the three gorges reservoir in less type, enhanced type, concentration, average 4 kinds of the process of rainfall infiltration under rainfall patterns and stability, and probes into the landslide tree change law of pore water pressure with time, and the tree landslide stability coefficient and the change of time relationship. Results show that the rainfall patterns of tree has distinct effect on the stability of landslide and rainfall infiltration, except under the condition of two levels continue to reduce the effect of the other two type less rainfall patterns under the condition of water level changes before the other three models, the change of water level to the influence of changing rainfall patterns of water level; Rainfall patterns and water level changes of rainfall infiltration under the dual role of also obvious changes have taken place; Initial landslide safety coefficient is above 1.2, and the safety factor of the landslide under the condition of two dropped below 1.2, especially landslide safety coefficient under the model of weakening the largest decline.