Abstract: Urgent effect of simulated acid rain sprayed on leaves of thirty herbaceous ornamental species was studied.The results show that the injured areas of foliar of ornamental plants are enlarged when the pH value of acid rain decreases.Foliar injury occurs in all of leaves treated with acid rain at pH 2.0,whose area is larger than 20 percent of leaf area in almost half species.There are three sensitive species,seventeen resistant species and ten secondary resistant species,which account for 10.0,56.67 and 33.33 percent of thirty herbaceous ornamental species,respectively.The injury threshold values of most plants are observed at pH 2.0～3.5 designed in this experiment.However,those of Brassia campestris,Viola tricolors and Zephyranthes candida are not fixed at pH 2.0.It indicates that three herbaceous ornamental plants own astrong resistance to acid rain.The results show that the resistance of thirty herbaceous ornamental plants to acid rain is related to the change of pH value of leaf cell,showing that the change of pH value of leaf cell results in the appearant injury in leaf.