This study aimed to better understand the limited natural distribution of the endangered ornamental plant Amsonia orientalis Decne. by focusing on salt stress, a common limiting factor of plant growth. Plants were subjected to in vitro salt stress at concentrations between 25 and 150 mM. In general, shoot and root lengths, root number, and total protein, chlorophyll a and carotenoid content were negatively influenced at NaCl concentrations above 25 mM. Hydrogen peroxide, malondialdehyde and proline content all gradually increased with increasing salt concentration. Activity levels of the antioxidant enzymes catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) were all at their maximum in plants cultured in medium containing 50 mM NaCl. Compared to control cultures, an overall upward trend in POD activity was observed with increasing salt concentration, while the activity levels of SOD and CAT increased at lower concentrations but were limited at elevated concentrations of NaCl. These results suggest that A. orientalis prefers soils with no or very low salt but can tolerate NaCl up to a concentration of 50 mM.