Samples of dustfall collected from the surfaces of wall paintings and painted sculptures in Mogao Grottoes, were analyzed as to physical and chemical properties, such as particle size distribution, chemical composition, microscopic morphology and soluble salt content. In addition, the influences of dustfall on wall paintings and painted sculptures in Mogao Grottoes were further studied. The results of the study show that 1) most of the dustfall deposited on the surfaces of wall paintings and painted sculptures in Mogao Grottoes is the crustal source mineral; 2) the potential harms to wall paintings and painted sculptures in the grottoes are physical covering and abrasion and 3) over long periods of time, dustfall will bring potential chemical threats, such as salt erosion, to wall paintings and painted sculptures. Dustfall on the surfaces of wall paintings and painted sculptures in Mogao Grottoes is an important factor that cannot be ignored as a cause of disease of wall paintings and painted sculptures. The results of the study provide basic data for the preventive conservation of wall paintings and painted sculptures in Mogao Grottoes.