Numerical classification and delimitation of eroded soils in Guyuan county,Ningxia autonomous region were studied by means of the principal components and stepwise discriminatory analysis based on the data from the field observation and nemerical coding.In this study,84 different eroded soil samples were collected and analysed and four important factors which Rnfluenced soil erpsion were used as variables for calculation.On the basis of grouping of intensities of the erosion factors,the intensity values for every eroded foil were used as observable values of the variables.Through stepwise discriminatory analysis,the types of 17 soils among 84 eroded soils are adjusted,furthermore the discriminatory equations are established.The key of eroded soil types is compiled based on the data calculated from the equations.The types of eroded soils can be discriminated and development tendency of soil erosion can be predicted with the add of the key.The study on eroded soils by means,of principal components reveals the relationship between eroded soil types and principal erosion factore;and on the basis of this study a delimitation scheme of eroded soil regions is suggested.