Abstract: This study aims to test the stress effect of simulated acid rain (pH 2.5, 4.5, 5.6)on the photo-physiological characteristics of three native herbaceous plants (Eupatorium chinense Linn., Paederia scandens (Lour.) Merr. and Wedelia chinensis （Osbeck.）Merr.). The results indicated that leaves of the three herbaceous plants showed injury under severe acid rain stress (pH 2.5). Leaves of E. chinense and P. scandens were damaged obviously and the damage area was between 5% and 10%, while that of W. chinensis was damaged slightly and the damage area was lower than 5%. Meanwhile, the three herbaceous plants showed different photosynthetic responses to simulated acid rain. With the decreasing pH, the chlorophyll (Chl) content and net photosynthetic rate (Pn) of E. chinense were both reduced, P. scandens had no significant difference in the Chl content, but its Pn was inhibited, while the Chl content and Pn of W. chinensis both had a trend of rising. Under severe acid rain stress, the activity of superoxide dismutase (SOD) and peroxidase (POD) increased in all three plants to varying degrees, which showed some resistance to acid rain. The present results indicated that W. chinensis showed a strong resistant to the acid rain than the other two herbaceous plants.