Abstract: There are many earth-structure sites in the arid areas of Northwest China, some of them are world cultural eritages. But it is regretful that they were eroded and deflated under the specific climate in the areas and damaged are very seriously. It is fairly necessary to study reinforcement of the earth-structure sites. Potassium silicate is an inorganic cementing-reinforcing material of aqueous solution. In this paper, a reinforcing technique for ancient earth-structure sites is described in detail and the mechanism for the reinforcement is preliminarily discussed. On the bassis of our practice, we conside that the potassium silicate is an effective material for reinforcement of earth-structure sites in the arid Northwest China and has an ideal effectiveness. It should be put into practice in the future.