The simulation experiments were carried on the influence of acid rain on a kind of famous fruit tree-longan. Results showed that acid rain could do damage on the leaf and tip of longan tree. Nutritional elements-K、Mg、P、Fe、Zn and Mn seeped and chlorophyll reduced. H⁺、Cl^- in acid rain were absorbed by cell that could do a lot of damage. The lower value of pH, the more harm. The situation of death would happen when the value of pH was below 3. Ca²⁺ had a trend for protection in transportation. A better way for reducing the harm of acid rain was to spray the mixture over the tree which was composed of 1.0 mg KH₂PO₄、 3.3 mg Ca(NO₃),42 g FeSO₄,29 g H₃BO₃ per miller. The concentration of mixture would not exceed 50 times. Acid rain could also do damage on the flower, bud and young fruit of longan tree to different degrees that flower was most, bud was second and young fruit was third. The mixture of 3.3 mg Ca(NO₃)₂,2.7 mg KNO₃,42 g FeSO₄ per miller which was sprayed on the young fruit could provide protection. Some measures such as fertile soil, good care of farm and enough nutrition for fruit tree would be a better way for reducing the harm of acid rain.