Abstract: Calcium sulfate whisker was prepared by low temperature atmospheric acidification method.The effects of 4 factors，such as proportion of gypsum and water，proportion of gypsum and sulfuric acid，dilute sulphuric acid′s dropping speed， and water bath temperature，on micro morphology of calcium sulfate whisker were investigated by single factor tests.The process parameters were also optimized by orthogonal test.The optimum process parameters were obtained as follows：gypsum and water ratio（mass ratio） was 1∶10，gypsum and sulfuric acid ratio（mass ratio） was 1∶5，dropping speed was 3 mL/min，and water bath temperature was 80 ℃.The purities of hemihydrate calcium sulfate whiskers and anhydrous calcium sulfate whiskers prepared under optimum conditions were 98.3% and 97.2%，respectively.Their slenderness ratios were 60 and 40 respectively，and both had good dispersion and uniform size.

Key words: calcium sulfate, whisker, slenderness ratio