Abstract: This paper examines ionic concentration of pollutants in air precipitation,through fall, stem flow and surface runoff of coniferous, broad-leaved forests and bare land. Results indicate that ionic concentration of different pollutants in air precipitation is in the following order:SO₄^2-＞NO₃^-＞Cl^-＞F^-;ionic concentration in throughfall and stem flow of coniferous forest and broad-leaved forest is significantly higher than that in air precipitation. Similarly, total ion in throughfall and stem flow is higher for the coniferous forest than for the broad-leaved forest.In both types of forest, SO₄^2- concentration in the pollutants is higher than the other ions, suggesting a higher dissolution of SO₂and acid depositions. These observations further show that “forests are filters of air pollutants”though the extent to which filtering occurs is a function of forest type.