Effects of leaching with simulated acid rain and low molecular weight organic acids on exchangeable bases of red soil were investigated using undistributed soil columns.The results showed that soil exchangeable potassium,sodium,calcium and magnesium in the 0-20 cm soil layer was increased by 5.19%-14.65% after the soils were leached with simulated acid rain 3.5 and 4.5 in pH,compared with check using deionised water.There was no significant difference in exchangeable potassium,sodium,calcium and magnesium in the 0-20 cm soil layer between Treatments Citric acid,Malic acid,Oxalic acid and Treatment Simulated acid rain,but the formers did show increase in the base ions by 10.42%-96.41% in the 20-50 cm soil layer,compared with the latter.The increase of soil exchangeable bases in the subsoil layer can be attributed to dissolution of minerals in the topsoil and leaching of base ions from topsoil.Leaching of base ions from topsoil was the prior mechanism in the study,which indicated that organic acids probably accelerate base ions leaching and soil acidification process.