In order to evaluate the responses of physiological indexes of Sonchus oleraceus to shortterm salt stress and provide theoretical instructions to the further research of salt tolerance and tolerance mechanism for wild plants, we irrigated S. oleraceus seedings with Hoagland’s nutrient solution containing NaCl at various concentrations［0 (control), 66, 133, 200, 250, 300 mmol·L^-1］. After 1, 2 and 3 day of salt treatments, the leaves of plants were harvested, Na⁺, K⁺, malondialdehyde (MDA), soluble sugar, soluble protein, free proline contents and superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were measured. The results showed that: (1) after 1, 2 day of 66~200 mmol·L^-1 NaCl，the changes of Na⁺ content were not obvious. K⁺ content and K⁺/ Na⁺ ratio significantly increased with salinity compared with CK and reached to the maximun at 200 mmol·L^-1 NaCl. After 3 day of salt treatment, the changes of K⁺ content had the similar tendency with 1 day and 2 day treatments. Na⁺ content significantly increased with salinity. K⁺/ Na⁺ ratio significantly decreased with salinity except at 66 mmol·L^-1 NaCl. (2) Soluble sugar, soluble protein and proline contents increased, then decreased with salinity after 1-3 day of salt stress. At 200 mmol·L^-1 NaCl, soluble protein content reached to the maximun after 1 day and 2 day salt stress and soluble sugar content reached to the maximun after 2 day and 3 day salt stress. Free proline had the similar tendency after 1 day and 2 day salt stress and significantly increased compared with CK with salinity after 3 day salt stress. (3) The activities of SOD, POD and CAT increased then decreased with salinity after 1~3 day salt stress. All of them reached to the maximun at 250 mmol·L^-1 NaCl and were much higher than CK at all levels of salinity after 1 day and 2 day salt stress. The activities of SOD and POD reached to the maximun at 200 mmol·L^-1 NaCl after 3 day salt stress, during which CAT activity reached to the maximun at 250 mmol·L^-1 NaCl and were much higher than CK except at 250 and 300 mmol·L^-1 NaCl. It was demonstrated that S. oleraceus was very salt tolerant and could tolerance 66-300 mmol·L^-1 NaCl, as judged from the higher ability to absorb K⁺ and reject Na⁺ as well as the higher osmoregulation and antioxidant capacity, almost relieving the toxicity of Na⁺ and osmotic stress. But, the osmoregulation and antioxidant capacity decrease when NaCl concentration exceed 200 mmol·L^-1.