Abstract：Liquid phase silicon dioxide produced while reclaiming tail gas of solar polysilicon production by Siemens is not used in Asia Silicon industry (Qinghai), but directly put to landfill, which not only is a waste of energy and raw materials, but also pollutes the environment. Therefore, in view of energy conservation and environmental protection, the gas should be recycled. This paper studies the properties of liquid phase silicon dioxide produced while reclaiming tail gas of solar polysilicon production by Siemens in Asia Silicon Industry (Qinghai). It is shown that the major factors that influence the purity of silicon dioxide are the heating loss and the burning loss; in addition to an amount of water, the samples contain some amount of ash and volatile, coming mainly from the hydrolysis of silicon tetrachloride, as well as some silica-gel. The silica-gel will lose water and the product silicon dioxide powder when heated to a high temperature. When the silicon dioxide adsorbs a small amount of hydrolysis of silicon chloride on its surface, it will volatile when heated. With this kind of method one can get powders of 99.8% silicon dioxide. In the morphological observation, it can be seen that the particle size increases by agglomeration.