Abstract: The physical and mechanical parameters of ore body and surface clay are measured. Then these parameters are inputted into SoilVision software to analyze seepage process and calculate slope stability coefficients of ion-absorpted type rare earth mine. The phreatic line and development of crack width of test ore block are monitored. The monitoring results show that the numerical calculation model is reasonable. The simplified model of slope is established in terms of the slope section shape and in-situ leaching mining technology features. The effect of deflector hole and collect liquid roadway to slope stability is discussed. The simulation calculations and experimental results indicate that the effect of deflector hole to slope safety factor is very small when charge liquid rate of deflector hole is less than 13.35%.The slope safety factor almost increases linearly with increasing charge liquid rate if charge liquid rate of deflector hole is 13.35% to 15.8%.For 42m horizontal long slope, collect liquid roadway plays an important role in controlling the slope instability if the distance between collect liquid roadway and seepage face is 12m to 24m.