In this paper，the process of directly preparing industrial grade aluminum fluoride by using fluorosilicic acid and aluminum hydroxide，a by-product of wet-process phosphoric acid was studied and optimized in order to improve the quality of aluminum fluoride products.It not only made full use of fluorine resources and optimized the synthesis process，but also focused on the study of adding polyethylene glycol（PEG） to improve the apparent density of aluminum fluoride products.The results showed that when the preheating temperature of fluorosilicic acid was 80 ℃，the mass fraction of fluorosilicic acid was 19.1%，the molar ratio of n（aluminum hydroxide）∶n（fluorosilicic acid） was 1.8∶1，the dry powder of aluminum hydroxide was rapidly fed，the reaction temperature was 95~107 ℃，the stirring speed was 400 r/min，the reaction time was 16 min，aluminum fluoride was added as seed crystal，the crystallization time was 5.0 h，and the crystallization temperature was 107 ℃，the yield of aluminum fluoride was 77.56%，and the apparent density of aluminum fluoride was 0.70 g/cm³.Aluminum fluoride was prepared by using polyethylene glycol as a crystal modifier.When the amount of polyethylene glycol was 7.40%，the crystallization time was 5.0 h，the crystallization stirring speed was 200 r/min，and the crystallization temperature was 107 ℃，the yield of aluminum fluoride was 81.45%.The apparent density of aluminum fluoride reached 0.83 g/cm³，and the apparent density was increased by 18.57%.The chemical composition and physical properties of aluminum fluoride products could meet the requirements of GB/T 4292—2017 “aluminum fluoride”.In this paper，the process of wet preparation of aluminum fluoride by fluorosilicic acid was optimized by using fluorosilicic acid and industrial grade aluminum hydroxide as raw materials，which improved the yield and apparent density of aluminum fluoride products，and provided technical support for the popularization and application of fluorosilicic acid，a by-product of phosphorus chemical industry.