Abstract: The three dimensional Eulerian long-range acid deposition numerical simulation model for atmospheric pollutant transportation has been designed. With this model, a series of numerical experiments are introduced to investigate the effects of reduction of sources and background concentration on the wet deposition amount of SO₄^2-, results of which indicate that the non-linear response of the ground-level gas-phase SO₂ concentration and wet deposition amount to source emission and background concentration. Reducing SO₂ emission by 50% and NOx emission by 40 % results in the maximum reduction percentage（more than 50%） of the ground-level gas-phase SO₂ concentration. Only reducing the background concentration of pollutants results in relatively small reduction of the groundlevel gas-phase SO₂ concentration and the wet deposition amount of SO₄^2-, however, further reducing source emission will result in obvious reduction.