In order to study the effects of acid rain on seed germination and seedling growth of maize, the experiment was carried out with simulated acid rain at pH 1.0,2.0,3.0,4.0,5.0,6.0 and 7.0. The results showed that the indexes of seed germination and seedling growth of maize were inhibited and reduced by the decreasing of the pH value.The indexes of seed germination and seedling growth of maizehad no significant difference from CK with the pH value from 5.0 to 6.0（P＞0.05） and showed some resistance to acid. When the pH was below 5.0, maize seed germination and seedling growth of maize were sharply inhibited, and the indexes were significantly lower than CK（P＜0.05）.The maize didn’t shoot up at pH 1.0 at all. The results also showed that different pH simulated acid rain had a large effect on the seedling physiological indexes of maize, the activity of chlorophyll content, carotenoid content, protected enzyme（SOD, POD, CAT） content and the protective enzyme（PPO, PAL） content showed a decreasing trend with the increase of acid, while the relative conductivity and malondialdehyde（MDA） showed an increasing trend. According to the comprehensive results, we can draw the conclusion that the injury threshold value of acid rain was likely between pH 3.0 and pH 4.0.