Abstract: Water is the key factor which determines the distribution,development and maintenance of the vegetation on sand dunes in arid and semiarid region.Based on continuous observation on water content in different types of sand dunes around 8 km far from Dabqig,the dynamic spatiotemporal change of water content in sand dune soil had been studied.The results showed that the seasonal dynamic change of water content could be divided into four periods:the accumulating period in spring,the water-consuming period,the accumulating period in fall and stable period. In spatial distribution,the sand water content was as follows: moving dunesemi-fixed dunedune fixed by Artemisia ordosicadune fixed by Salix psammophila and A.ordosica.Vertical distribution of water content could be divided into the rapid change layer,active layer,and stable layer.The water content of leeward slope was lower than that of wilting coefficient,which was not suitable for planting,and the ground water level in inter-dune lowlands was high.