The invention relates to a method for preparing high purity silica white by using rice husk ash as a raw material, belonging to the field of fine inorganic chemical technology. The invention is characterized by comprising the following steps: taking the rice husk ash and water for washing under constant stirring, separation, pickling, leaching, and then undertaking washing till the lavage liquid is neutral and drying; taking the dried rice husk ash for being mixed and reacted with the sodium hydroxide solution, through leaching and washing; collecting filtrate and washing liquid so as to be condensed and obtain water glass; diluting the water glass which is obtained from the condensation and adding metal ion chelating agent, and next carrying out precipitation reaction after being fully dissolved, then a sediment is obtained by centrifugal separation; using ultrasound-assisted washing treatment, and then undertaking centrifugal separation and repeated washing; placing the washed sediment into a drying oven and then crushing and packaging the sediment so as to obtain the silica white product. The invention has simple process flow, easy operation, can improve the purity of the silica white, and is suitable for commercial process; moreover, the heavy metal content is less, which can completely replace or is even better than the market silica white product and also eliminates the environmental pollution of the rice husk ash.