From the viewpoint of soil genesis,some natures existing in the process of soil formation are discussed after expounding the important functions of organisms, especially plants in the process of soil formation, development and evolution. Thus it is proved that mobile sand dunes are only non-soil materials affected, by geological function or parent materials, but not soils. Onthe basis of above analysis, the formation, development and evolution direction of the soil on mobile sand dunes and its position and naming in soil classification are approached.