The invention discloses a method for preparing white silica gel from potassium feldspar and belongs to the field of chemical production. The method comprises the following steps: mixing potassium feldspar powder and a nitric acid solution, and carrying out microwave hydrothermal pre-treatment; then, mixing the potassium feldspar powder subjected to the nitric acid microwave hydrothermal pre-treatment with a KOH water solution, and carrying out microwave hydrothermal reaction; filtering, washing and drying to obtain acid-soluble potassium aluminum silicate rod-shaped particles; dissolving the obtained acid-soluble potassium aluminum silicate rod-shaped particles into a sulfuric acid solution and carrying out microwave hydrothermal treatment; filtering, washing and drying to obtain the white silica gel. Compared with an existing potassium feldspar comprehensive utilization technology in the prior art, the reaction time is shortened, and the reaction temperature, the KOH concentration and the acid concentration are reduced, so that the production cost and energy sources are saved; meanwhile, the corrosion of the potassium feldspar to equipment in a comprehensive utilization process is also greatly reduced and industrial production is expected to realize.