A systematically monitoring has been carried of soil percolating water in karst stony desertification area.The result showed that higher the degree of stony desertification is,the higher the concentrations of HCO^-3,Ca²⁺ and the value of calcite saturation index(SI_C) in the percolating water from rendzina area are.The concentrations of Mg²⁺ in water samples from yellow soil area showed the same trend.It maybe result from related soil and vegetation degradation.When vegetation degradation starts earlier than soil,the concentrations of HCO^-3,Ca²⁺ will decrease with the development of stony desertification due to the stronger reactions between water and soil.On the contrary,when soil degradation starts earlier than vegetation,the concentrations of HCO^-3,Ca²⁺ will increase with the development of stony desertification due to more time requirement for reactions between water and soil.