Abstract: In order to study the influence of rainfall infiltration on the stability of unsaturated soil slope，based on saturated-unsaturated seepage theory，the change of seepage field in slope and its influence on the slope stability under rainfall infiltration are analyzed.The study results show that:①rainfall infiltration is a saturated-unsaturated process，and its internal volumetric water content changes dynamically with the change of rainfall duration，in the initial stage of rainfall，the soil is in unsaturated state，the cohesion increases with the increase of water content，and the variation of internal friction angle is small，its overall trend is downward，with the increase of matrix suction and safety coefficient，which is beneficial to slope stability；②with the continuous rainfall，pore water pressure changes from negative to positive，cohesion and internal friction angle decrease with the increase of water content，matrix suction weakens，and slope stability decreases；③the final process of rainfall infiltration is the rise of internal water level，the increase of dynamic and static water pressure，and the decrease of effective soil weight，the soil softens， the mechanical strength parameters decrease，and the stability of the slope decreases，the permeability coefficient of the soil is inversely proportional to the safety factor of the slope as a whole.Based on the above discussion results，combined with the example of soil slope，the strength reduction method is used to reveal the change rule of the potential slip surface and the peak displacement of the slope along with the rainfall duration time under the condition of rainfall infiltration.The results indicated that the potential sliding surface at the beginning of rainfall increases from shallow to deep，and the peak displacement increases continuously；after the rainfall stopes，the stress in soil is re-distributed，the soil changes from saturated to unsaturated，and the potential sliding surface and peak displacemenet change inversly.In order to prevent the slope from destabilizing and destroying by rainfall，the rationalization treatment suggestions of soil slope are put forward， which provides a reliable reference for the comprehenisve treatment of unsaturated soil slope.

Key words: Open-pit mining, Unstatured soil, Slope stability, Volume moisture content, Strength reduction method, Safety coefficient