The invention relates to a method for producing ethanol by adopting cassava, in particular to a desanding method used in process for producing ethanol by adopting cassava, which is characterized by comprising the following steps in production: feeding of sand-containing cassava into a feed bin, blending of sand-containing cassava starch, first-stage desanding separation, second-stage desanding separation, third-stage desanding separation, fourth-stage desanding separation and sand collection. The desanding method has the advantages of being capable of improving the removal rate of sand in the cassava material (the total removal rate of sand in cassava is only 30 percent currently, and the removal rate of sand is improved to be more than 95 percent), greatly reducing the loss of starch, saving water, improving the energy utilization rate, improving the ethanol yield, and greatly prolonging the service life of alcohol production equipment. The treatment capacity of the sand-containing cassava starch after separation is greatly reduced compared with the material treatment capacity of other desanding technologies, and the desanding effect is greatly enhanced, and the desanding cost is reduced. the method has remarkable technical progress.