Abstract: ObjectiveThe influence of acid rain stress on photosynthesis and physiological indexes of Atractylodes lancea(Thunb.) DC. was investigated,so as to provide reference for anti-acid rain cultivation of A. lancea. MethodPot experiments were conducted, and acid rain stresses of different gradients were simulated on A. lancea. Photosynthesis and physiological indexes of A. lancea under acid rain stress were measured, and variation trends of the indexes under stresses of different gradients were compared and analyzed. ResultPhotosynthesis indexes of leaves of A. lancea varied at the ini-tial stage of acid rain stress. Net photosynthetic rate(Pn), stomatal conductance(Gs) and transpiration rate(Tr) presented an up-ward trend as a whole, while intercellular carbon dioxide concentration(Ci) presented a downward trend, showing a cer-tain adaptability to acid rain stress. After day 21 of stress, pH 2.0 and pH 3.0 treated Pn, Gs and Tr were high, and Ci de-creased. Pn,Gs and Tr treated by pH 2.0 and pH 3.0 decreased rapidly after day 28 of stress, and Ci increased rapidly. Varia-tion of photosynthesis index in pH 4.0 and pH 5.0 treatment was slow. With the extension of acid rain stress, the activities of three kinds of antioxidant enzymes, malondialdehyde(MDA) and free proline(Pro) in leaves of A. lancea were first increased and then decreased. Superoxide dismutase(SOD) activity on day 15 of stress reached the maximum value, and peroxidase(POD) and catalase(CAT) activity reached the maximum value on day 22. As acidity of acid rain increased, the variation range of indexes were more obvious. ConclusionThe threshold value of acid rain for A. lancea leaf is about pH 3.0,and the acid rain under pH 3.0 has significant effects on growth and development of A. lancea.