From the aspects of physics and chemistry,the process and characteristics of soil quality degradation in Guizhou karst area were discussed.Results showed that in the rocky desertifcation process of soil,a series of physical and chemical properties worsened associated with losses of soil fine particle materials,including bulk density raised,total porosity reduced,aeration and non-capillary porosity increased,water-holding capacity relented,soil organic matter,total N and P contents decreased.the majority of silt and clay contents(<0.05 mm) were removed,could result in the decreases of soil organic matter and total N contents.Dusiturbances induced by farmers(i.e.irrational land cultivation and vegetaion was destroied) was the main force of soil quality evolvement.The models of soil quality degaradation process was gradual degradation course and leap degradation course.