Abstract: The process conditions of the reaction between nitric acid acidolysis solution of Kunyang phosphorite and ammonium sulfate to produce calcium sulfate were studied.Effects of the amount of（NH₄）₂SO₄，mass fraction of（NH₄）₂SO₄，reaction temperature，feeding time，and reaction time on the size of crystal and the co-crystallized phosphorus content were investigated.The optimal process parameters of the reaction were obtained as follows: the amount of （NH₄）₂SO₄ was 110%，mass frac- tion of（NH₄）₂SO₄ was 30%，reaction temperature was 90 ℃，feeding time was 20 min，and reaction time was 2 h.Under those conditions，the crystal contained 0.179%（mass fraction）phosphorus and 0.06%（mass fraction） fluorine，in mixture form of calcium sulfate hemihydrate and calcium sulfate dihydrate was obtained，which had the advantages，such as uniform and bigger crystal shape and high filtration rate.

Key words: nitric phosphate；calcium sulfate, ammonium sulfate；crystallization