The invention discloses a method using phosphogypsum as the raw material to produce ammonium sulfate, and the method comprises steps as follows: 1750 shares of crude phospho gypsum which contains 20 percent of free water is taken, and 2 to 5 percent of the amount of the crude phospho gypsum of activator is added the aging for 2 to 8 days; then, a reaction tank and an ammonium carbonate solution are added to carry out the conversion reaction, in the reaction process, the concentration of the ammonium carbonate solution is 40 to 42 percent, the carbonized ratio CO2/2NH3 is 1.34 to 1.37, the quality is 1840 to 2000g, the reaction temperature ranges from 55 to 70 DEG C, the stirring speed ranges from 200 to 240 turns per minute, and the reaction time ranges from 1.5 to 2.5 hours; after filtration, the ammonium sulfate solution is obtained, the ammonium sulfate solution is neutralized by sulfate to obtain a PH value ranging from 6.9 to 7.02, and then, an ammonium sulfate excellent grade product is obtained through multi-effect evaporation crystallization and drying. The method can solve problems of waste piling and pollution of phosphogypsum, which restrict the development of the phosphate chemical industry, and realize the resource utilization of the phosphogypsum.The production cost is low, and the industrial production can be realized.