Abstract: Potassium feldspar was decomposed in the presence of fluorite accessory ingredient and sulfuric acid，and the solid decomposition products were used to prepare calcium sulfate whisker by atmospheric acidification method.The influences of amount of sulfuric acid，reaction temperature，solid to liquid ratio，reaction time，and amount of additive on the preparation of calcium sulfate whisker were studied.Results showed：under the conditions of reaction time of 60 min，reaction temperature of 103 ℃，mass ratio of solid，sulfuric acid，and water of 1∶4.4∶35，and amount of magnesium sulfate additive of 0.12 g（2.4% of the raw material），the final product′s yield，slenderness ratio，white content，and purity were 27.36%，65，65.3%，and 95.61%， respectively.

Key words: potassium feldspar, calcium sulfate whisker, atmospheric acidification method, slenderness ratio