The quantitative relationship between gobi sand transport amount and drift potential is still a key scientific problem in the subject of both aeolian geomorphology and sand controlling engineering. By monitoring the sand transport rate over gobi surface above the Mogao Grottoes from May 2008 to April 2009, the characteristics of sand transport under complex wind regimes and different sand sources were studied. The results show the drift potential (DP) in the region is 129 VU. The calculated total sand transport rate over the northern gobi above the Mogao Grottoes is 905 kg·m^-1 or so, of which 500 kg·m^-1 is transported by easterly winds, while 320 kg·m^-1 is blown by westerly winds. When the wind velocity is bigger than 11 m·s^-1, about 265 kg·m^-1 of sands are transported from the Mingsha Mountain to the top of grottoes by westerly winds, and 410 kg·m^-1 of sands are blown back to the Mingsha Mountain by easterly winds. Based on the above results, it is feasible to block sand coming from the Mingsha Mountain and to remove the intercepted sand from moving back to the Mingsha Mountain as well as to construct an artificial gobi bed on the top of the Mogao Grottoes.