Soil and water loss in expressway is representative type of man-made accelerated erosion.The type,situation and intensity of soil and water loss have direct relation to the construction of principal part of the expressway.The eroded environment is composed of erosive forces system,eroded object and eroded unit.Soil and water loss showed discrete distribution along the expressway in space and have great identities with the construction of principal part in time.Based on it,the eroded units and soil and water loss characteristics in the scope of duty on prevention of soil and water loss were studied on classification by surveying different expressways in which some have been completed,some are under the construction and some are planned to be built in Chongqing.Besides the features of harmful geology structure stability along expressway and the key dominant factor were discussed on classification.At last the environmental sensitive area in expressway also was discussed to provide theoretical support for prediction of soil and water loss,arrangement of soil and water conservation measurement and monitor of soil and water loss.