Abstract: Using the data recorded by the automatically meteorological stations around the Crescent Moon Spring, combined with the result of simulating the mountain and valley breezes by WRF-LES model to analyze the wind field and sand transport in this area. The results show that: ① There are three main wind streams in Dunhuang every year. They are northwest wind, northeast wind and south wind. The influence of these three kinds of wind balance out each other, keeping the sand dunes in this area stable;② The sand movement is stronger in spring and summer and more intense in the peripheral region of Crescent Moon Spring. When the winds pass through the Spring, the acting time of sand driving wind will reduce percent 30 to percent 40.The terrain changes the direction of sand driving wind and in the same time the wind energy disperses, the velocity of the wind slows down and the sands in the wind will be left in the valley;③ The simulation results prove that: With only influence of the solar radiation, the wind direction will reverse between day and night in the research field. It’s a phenomenon of down-valley wind. The specific heat capacities of water and sand are different, which makes the temperature of lake and dunes different from each other either in day and night. It forces high pressure and low pressure to appear in the boundary layer. The high pressure and low pressure cause the down-valley wind finally. Between the down-valley wind and mountain wind, the mount wind has larger contribution to the sand transportation. Average velocity of the mountain wind is 0.767 m·s^-1, from the lake to both north and south. With the influence of this kind of mountain wind, the total sand discharge from the lake to outside increase percent 8.48.

Key words: wind field, sand transport, WRF-LES model, mountain and valley breezes, Crescent Moon Spring scenic spot, Dunhuang