Instability mode of soft rock slope in rainy condition is one of bases for slope disposal. In order to research the stability of soft rock slope under rainfall infiltration

this article put forward a new method which not only can consider the impact of seepage field on the slope stability but also can reflect the adverse effect on the slope instability caused by rock softening effect. Two-dimensional seepage numerical calculation method is used to simulate the slope pore water pressure size and the distribution of transient saturated zone area on space and time in rainy condition. Combined the seepage field calculation results with the value of physico-mechanical parameters of rock which are obtained from transient saturated zone area soften rocks test versus time

and strength reduction method is used to analysis the stability of soft rock slope under rainy infiltration condition. The research of example slope indicates that: in early rainfall period the representation of soft rock slope instability is the local layered collapsing of slope surface under rainy infiltration condition. With the growth of rainfall duration

the representation form of the instability is the combined local layered collapsing with whole sliding. After rainfall stopping

the recovery of slope negative pore water pressure has certain delayed effect for the continuous reduction of safety coefficient of soft rock slope.