A preparation process of potassium sulfate was introduced, i.e., the reaction of potassium chloride with ammonium sulfate to produce potassium ammonium sulfate and potassium ammonium chloride, and then the reaction of potassium ammonium sulfate with potassium chloride solution to produce potassium sulfate. The process flow, main process and process parameter control, product content, energy consumption and equipment material recommended by this process were described in detail. The K2O mass fraction of the product was ≥50% and the K2O conversion rate was more than 70%, which meets the national standard of potassium sulfate for agriculture. Compared with the traditional multiple decomposition process, this process has higher product purity, higher potassium conversion rate, shorter process route and lower energy consumption, and has good social and economic benefits.