Abstract: Under the influence of geomorphology, climate and hydrology, rock and soil characteristics, local geology and so on, the rock masses forming the northern Mogao Grottoes in Dunhuang have formed several types of variations and deformations. The variations include surface weathering and load discharging. The deformations contain rock fall, crag and collapse, split and crannies (structural cranny, discharged cranny, horizontal cranny and vertical cranny) due to artificial digging, gravity, wind erosion, rain erosion and flood erosion. These variations and deformations have generated great dangers to grotto safety and stability of the rock mass. Using potassium silicate material and coal ashes, the crannies are grouted and the surface weathering layers are sprayed. The variations and deformations of the rock masses and surface weathering have been decreased. The rock masses are reinforced and the grottoes are well protected. The method is an effective reinforcement countermeasure for cultural relic protection in the loess and arid region.