The invention relates to a method for producing potassium sulfate by using low-concentration fume sulfur dioxide, and belongs to the technical field of chemical engineering and environmental protection. The method comprises the following steps: absorbing ammonium sulfate solution produced by SO2 by using industrial potassium chloride and the ammonia process to continuously charge according to the mass ratio of KCl/(NH4)2SO4 equal to 1.05 to 1.1, wherein the charging time is 90 to 120 min, the reaction time is 30 min, the stirring rate is 150-200 turns/minute, the liquid to solid ratio L/S is equal to 1.2 to 1.3, the reaction temperature is 28 to 35 DWG C, the concentration of solution K<+> is controlled with the scope of 58 to 68 g/L; adding 5 to 7 percent of 100 to 200 meshes of potassium sulfate inoculating crystal according to the output of K2SO4 after charging for 10 min, filtering after the completion of reaction, and vaporizing filtrate after being filtered to obtain byproduct m NH4Cl.KCl fertilizers; flushing a filter cake by using 12 to 17 percent of KCL solution, wherein the lotion amount is 15 to 20 percent of volume flow rate of total reaction liquid, pumping the filter cake again, and cleaning the filtrate and charging again; and measuring a product K2SO4 by deducting the amount of the innovating crystal added after the filtrate is dried. The invention has the advantages of reduced evaporated crystal during the (NH4)2SO4 solution and dissolution process of a (NH4)2SO4 solid, short flow, save energy consumption, prolonged desulfurizing industrial chain, and produced national deficient products, and has better economic and social benefit.