Abstract: The locse surface material composition of sandy land is one of the important natural factors in the formation of desertification,especially when the sand particles account for about 75% of the total mechanical composition. There has been a few patches of shifting dunes in the Ningxia-Shaanxi loess hilly region but their total area is very limited.In the sections occurring shifting sands the fine sand particles constitute more than 60 per cent in soils while in the vast area of loess hilly region no shifting dunes occur,because the average sand particles amount to only 34.6 per cent. They only occur in local places where the sand particles account for more than 60 per cent.