Puding County is one of the most serious regions suffering from soil and water loss in Guizhou Province.The area of soil and water loss in the county is 60.8% of the total land area and the soil erosion modulus is 4422.3t/(km²·a).The development of karst fissure,sinkhole,and underground river is found to be the main factor of soil and water loss through analyzing the field data,topographic characteristics,lithologic features,and hydrological condition.The models of soil and water loss and karst leakage are generalized and the relationships among raindrop splash,slope erosion,sinkhole leakage,and underground river transport in the processes of soil and water loss are studied.The mechanisms of soil and water loss in karst area are analyzed as well.The study has a certain signification to prevent soil and water loss in this area.