With reference to the recent data on neoteetonic movement in Sony-Liao Plain, the author suggests that the genetic differences between the cultivated black soil and the light chernozem are mainly determined by their parent. materials and age of soil formation. The former is derived from the sediments of middle Pleistocene on the undulating or rolling terraces and characterized by abundant humus and non-calcareous reaction;and the latter is developed on alluviumof late Pleistocene or recent alluvial deposits in the central flat part of the plain and characterized by less organic matter and strongly calcareous reactioa. The latter is much more infant than the former, and it has been formed along a sequance of swamp-meadow soil-meadew light ehernozem-light chernozem.Under the present climatic conditions, the genetic direction of the meadow soil types is constrained by their vegetative cover. Once their vegetative covers are destroyed by either natural or artifical causes, with the evaporation being intensified the soda solonchak or solonetz will be formed even under the condition of slightly mineralized ground-water. From the viewpoint of soil formation, the principle of rational use of alkaline grassland and reclamation of soda solonchak should be the protection and restoration of vegetative covers of the soils.