Abstract: The α-hemihydrate gypsum（α-HH) was prepared by aqueous salt solution method at atmospheric pressure using flue gas desulfurization gypsum from Shandong Huaneng Power Plant.Effect of crystal modifier type，such as adipic acid，citric acid，ethylenediaminetetraacetic acid(EDTA)，succinic acid，oxalic acid，on the crystal morphology of α-HH was studied.The results show that when NaCl salt solution concentration of 20%，gypsum slurry concentration of 20%，natural pH，reaction temperature is 95 ℃，optimum reaction time is 3 h，the crystal morphology is change by five organic acid crystal modifier .The crystals morphology is unsatisfactory with adipic acid，citric acid and oxalic acid as crystal modifier，but the crystals morphology is perfect with the succinic acid dosage is 0.04% and EDTA dosage is 0.07%。XRD analysis results showed the products is α-HH，and TEM analysis results indicated the quality of crystal is better when adding 0.04% succinic acid than 0.07% EDTA.

Key words: FGD gypsum, α-hemihydrate gypsum, Crystalline morphology, Crystal modifier