The invention relates to a potassium sulfate abstracted from sintered dust removing ash and a preparation method thereof, and belongs to the technical field of a chemical product. The preparation method comprises the following steps: weighing the dust removing ash, adding the dust removing ash in water with the weight being three times than that of the dust removing ash; dipping the dust removing ash for three days at the normal temperature; filtering the dust removing ash; concentrating filtrate to one tenth by adopting the reduced pressure distillation method; analyzing the content of K<+> in concentrated solution; adding ammonium sulfate in the concentrated solution, so that the K<+>: SO4<2+> is equal to 2.1:1 in the solution; adding formamide again; reacting for two hours at the temperature of 80 DEG C; and then obtaining potassium sulfate crystal. After the potassium sulfate crystal is filtered and dried, the potassium sulfate product can be obtained; the filtrate is distilled at the temperature of 90 DEG C; an organic solvent added is recovered; and distillation residue is returned to a potassium sulphate composite reaction system to be recycled. By utilizing the metallurgical sintered dust removing ash, the invention has the advantages of simple process, low energy consumption, high return rate of kali salt, not only improves the availability of high resources and protects the environment, but also has better economic benefit and is a green and environment-friendly recycling economy project.