The invention relates to a method for desanding powder slurry. The method is characterized in that sands-containing powder and a sands-containing solvent is provided in a feed mixer, then the powder and the solvent are mixed to prepare the powder slurry; the powder slurry is transported into a sand removing machine for separating the sands from the powder slurry, the sands and the powder slurry without the sands are respectively discharged from a sand outlet and a discharge port of the sand removing machine, and the spraying an eluting solvent by reversing to the sand discharging direction of the sand outlet. The method can effectively separate sands and the powder slurry, the powder slurry carried with the sands can be separated by a back flushing device, so that the effects of low energy consumption and high separation efficiency can be simultaneously satisfied.