Through the analysis on physical and chemical characteristic of the desulfurization by-products of amine additives in a steel mill,the comprehensive utilization process is designed,the influence of different leaching processes on the leaching rate of S and K is investigated, the experimental research of one-step preparation of potassium sulfate by ammonium sulfate is carried out ,and the feasibility of potassium-containing compound fertilizer is discussed. The results show that the optimum leaching process parameters are as follows: temperature of 35 ℃ , stirring time of 30 min,solid-liquid ratio of 1:4 , stirring speed of 200 r/min and grinding particle size is less than 74 μm. At this time, the leaching rates of S and K are the best, 85.23% and 97.05% respectively. Meanwhile,potassium sulfate products with K₂O mass fraction of 60.44% ,S mass fraction of 15.60% and Cl mass fraction of 0.57% can be prepared after evaporation, concentration, cooling and crystallization of filtrate, meeting the national standard requirements of agricultural potassium-containing compound fertilizer, indicating that the process is highly feasible.