Acid rain has become a serious worldwide environmental problem, and it negatively affects both crops in agricultural areas and garden plants in city environments. The aim of this study was to evaluate the tolerance of Rhododendron hybridum to acid rainwater to determine whether it is suitable for use as a landscaping plant in areas affected by acid rain. We conducted a series of pot experiments to study the effects of simulated acid rain on the growth and the physiological and ecological characteristics of R. hybridum. We used 3-year-old trees of R. hybridum var. "Zijinguan" as the experimental materials. The leaves were sprayed with simulated acid rain (pH=2.0, 3.0, 4.3, or 5.6) or tap water (pH=6.5) as the control. The plants were sprayed once every 7 days, until the leaves were saturated with the liquid, for 2 months. We evaluated the plants before the start of the experiment, after 1 month, and at the end of the experiment. We measured the chlorophyll (Chl) content, malondialdehyde (MDA) content, and soluble protein content, and determined catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activities in the leaves. At the end of the experiment, we evaluated the degree of leaf injury and photosynthetic indicators including net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intercellular CO₂ concentration (Ci), and water use efficiency (WUE). The results showed that under simulated acid rain stress, the leaves of R. hybridum were damaged more severely as the pH of the rainwater decreased. In the pH=2.0 rainwater treatment, there was a high rate of leaf abscission, some of the leaves turned red, many leaves were curled and withered, and the leaf injury was up to 33%. In the pH=3.0 treatment, the negative effects were smaller than those of the pH=2.0 treatment; there was 16% leaf injury, some of the leaves were yellow and wilted, and there was a moderate rate of leaf abscission. When the pH of the rain water was higher than 4.3, the damage was minimal and plants were able to grow normally. There were stronger effects of simulated acid rain on Chl content in R. hybridum leaves as the pH value decreased, and the negative effects of low-pH rainwater became greater over time. The Chl contents of plants in the pH=3.0 and pH=2.0 rainwater treatments were significantly lower than those of leaves of control plants. In all of the acid rain treatments, the MDA content of R. hybridum leaves gradually increased during the experimental period; the soluble protein content first increased and then decreased. The activities of CAT, POD, and SOD showed a single-peak curve, first increasing and then decreasing during the experimental period. The highest CAT and SOD activities were detected in leaves of plants in the pH=4.3 rainwater treatment while the highest POD activity was detected in leaves of those in the pH=3.0 rainwater treatment. The Chl content gradually decreased in all of the acid rain treatments. The Pn, Tr, Gs, and WUE showed trends to first increase, and then decrease, during the acid rain treatments. The Ci steadily decreased in all of the acid rain treatments over the 2-month experimental period. The maximum values for Pn, Tr, Gs, and WUE were in plants in the pH=4.3 treatment. Based on the above results, we conclude that a rainwater pH of 3.0 is the threshold for damage to R. hybridum. The pH of rain in areas badly affected by acid has an approximate range of 2.0 to 4.0. Our results show that R. hybridum can grow and be used as a landscaping and vegetation construction plant in some acid rain-hit areas.