Effects of soil leaching with simulated acid rain and several low molecular weight organic acids on leaching loss of Al, Si and base ions from red soil were investigated in a simulated leaching experiment with 50 cm undistributed soil columns. Results showed that little Al, some Si and base ions were leached out from the soils with simulated acid rain. Compared with that in CK, using deionised water for leaching, the content of Si leached out was increased by 6.52% and 3.26%, and contents of K⁺、Na⁺、Ca²⁺、Mg²⁺ by 2.41%~96.80%, after the soils were leached with acid rain of pH 3.5 and pH 4.5. The contents of Al and Si leached out in the 100μmol/L citric acid, malic acid, oxalic acid treatments were similar to that in the simulated acid rain treatment; while those in the 10 mmol/L citric acid, malic acid, oxalic acid treatments were increased remarkably. The total content of base ions leached out in the organic acid treatment was 1.58~9.27 times that in the simulated acid rain treatment, suggesting that low molecular weight organic acids are probably greater contributors to soil acidification than acid rain.