The invention provides a preparation method of an ionic liquid for absorbing SO2, and an application of the ionic liquid in absorbing SO2. The preparation method of the ionic liquid comprises the steps of uniformly mixing one of aluminium chloride, zinc chloride, lithium chloride, aluminum sulfate, zinc sulfate, lithium sulfate, aluminium nitrate, zinc nitrate and lithium nitrate with one or two of urea, propanamide, butyramide, caprolactam, N,N-dimethylformamide and N,N-dimethylacetamide at a molar ratio of 1:(1-10) or 1:(0.5-3):(1-7), conducting reaction for 1-10h at 70-150 DEG C, conducting vacuum drying on an obtained solution at 40-60 DEG C, and obtaining the ionic liquid. The ionic liquid is mainly used for quickly and efficiently absorbing SO2. With the adoption of the ionic liquid as an SO2 absorbent, requirements on equipment required for absorbing SO2 are simple, the operational conditions are mild, the absorption efficiency is high, the cost is low, the ionic liquid can be recycled, and waste liquid and waste water discharge and other problems do not exist, and the ionic liquid is suitable for industrial production, meets the requirements of green chemical development of the contemporary society, and has good economic and social benefits.