Simulated acid rain reduced pH of orchard soil and aggravated acidification of the soil. Compared with CK, the orchard soil decreased by 0.23, 0.54, 1.22 and 1.79 in pH, by 0.01~0.08 cmol/kg in content of exchangeable K, by 0~0.08 cmol/kg in content of exchangeable Na, by 0.14~0.31 cmol/kg in content of Ca, and by 0~0.10 cmol/kg in content of exchangeable Mg, but increased by 0.22%, 14.33 %, 41.41 %, and 66.38 % in content of active Al. Treatment of MgSO₄, CaCl₂, KH2PO₄ and citric acid could reduce leaching of active Al and base ions from the soil and inhibit Longan saplings from absorbing Al. Treatment of 2 mmol/L Mg²⁺、Ca₂+、PO₄ 3- and citric acid reduced the content of Al in roots, stems, and leaves, by 13.9 %~39.2 %, 16.9 %~39.7 %, and 30.1%~41.0 %, respectively, when Al concentration was 0.185 mmol/L, and decreased by 29.3 %~51.3 %, 15.3 %~39.7 %, and 16.5 %~42.5 %, respectively when Al concentration was 1.850 mmol/L.