The present paper deals with results of preliminary studies on the microbiological properties of the sand dunes in Tengkeli desert of Ninghsia province.It reveals the following facts:1.The relative number of microorganisms and the composition of microflora in the fixed sand dunes are quite different from those in the mobile sand dunes.Larger number of microorganisms with higher activity have been found in the fixed sand dunes than in mobile sands.It also indicates that the fixation of the sands under the influence of the growth of high plants is an essential factor in improving soil fertility.2.In the fixed sand dunes,more microorganisms with higher activity exist in soils of rhizosphere of high plants.It shows that the root development of high plants has a significant influence to the microflora.3.A greater number of microorganisms also exist in the surface crust of sand dunes in comparison with the corresponding subsoils.The activity of microorganisms may give a definit affect on the formation of soil surface crust.The role of microorganisms in the process of fixing the sand dunes needs further investigations.