Nanyou 2 and Nanyou 3 are two cultivars of barbadosnut (Jatropha curcas L.) with different genotypes. Physiological and ecological responses of these two cultivars to salt stress were studied by comparing their tolerances to various concentrations of NaCl. When the seedlings were exposed to NaCl at 25 and 50 mmol?L-1, Nanyou 2 showed no change while Nanyou 3 decreased significantly in total dry weight. When treated with NaCl at 100 mmol?L-1 or higher concentrations, the total dry weight of seedlings of both cultivars decreased significantly, and Nanyou 3 decreased to a greater extent than Nanyou 2 did. Relative water contents of seedling leaves showed no changes upon treatment with NaCl at 200mmol?L-1 or lower concentrations, but a significant decrease by 5% and 8% in Nanyou 2 and Nanyou 3, respectively, upon treatment with NaCl at 300mmol?L-1. When treated with NaCl at 25 and 50 mmol?L-1, Nanyou 2 decreased significantly whereas Nanyou 3 showed no change in the soluble sugar contents. As the NaCl concentration increased to 200 and 300 mmol?L-1, the soluble sugar contents of both cultivars decreased significantly. Meanwhile, Nanyou 2 had a significant increase while Nanyou 3 showed no change in the soluble protein contents. The SOD activity of Nanyou 2 displayed an increase-decrease curve as the NaCl concentrations increased, and, upon treatment with NaCl at 300mmol?L-1, it was significantly lower than the control plants. The SOD activity of Nanyou 3 decreased steadily as salt concentrations increased and was significantly lower than the control plants in all treatments. The POD activities of both cultivars showed no differences with the control plants as treated with 25 and 50 mmol?L-1 of NaCl. As the NaCl concentrations increased, POD activity of Nanyou 2 increased and that of Nanyou 3 decrease significantly as compared to corresponding controls. The CAT activities of both cultivars increased significantly when treated with NaCl at 25 and 50 mmol?L-1, and then showed similar trend as the SOD activities did in both cultivars respectively as the salt concentrations increased. These results suggested that barbadosnut seedlings were salt tolerant, and the Nanyou 2 was more tolerant than Nanyou 3, mainly due to its higher protective enzyme activities, ability to maintain higher leaf water contents and higher soluble protein contents upon exposure to salt stress.