White oblique crystals, industrial products are white or light gray lumps or rods. Easily soluble in water, emits a lot of heat of dissolution when dissolved, soluble in ethanol, slightly soluble in ether. It is deliquescent and has strong water absorption.

Potassium hydroxide is strongly alkaline and corrosive, and its properties are similar to sodium hydroxide, which can cause burns. It can absorb water and dissolve in the air, and absorb carbon dioxide to gradually become potassium carbonate. The pH of the 0.1 mol/L solution is 13.5.