The ordering characteristics of soil erosion class, in particular those in 5 and 7 band of LANDSAT MSS CCT image, were introduced, and the principle and operational procedure for soil erosion mapping by it were presented in this paper. The soil erosion map and the area of each class in the experimental region obtained by using the method were in good agreement with the results by conventional investigation, The main measures to ensure high accuracy and the low cost for the method are discussed, and it is considered that this method will have great prospect in practice and research on soil erosion mapping.