In order to clear the saltadaptive mechanisms of photosynthesis and physiobiochemistry of different peanut varieties in salt stress, we conducted pot experiment by setting 0, 1.0, 2.0, 3.0 g/kg NaCl concentration gradient, and tested the physiological index of salttolerant peanut varieties (HY25, LH12) and saltsensitive varieties (HH1, HY20), including photosynthetic traits (photosynthetic rate, apparent quantum efficiency and stomatal conductance), antioxidant enzyme activities and contents of osmotic regulatory substances. The results showed as follows. (1) The NaCl stress significantly inhibited photosynthesis of peanut leaves. The net photosynthetic rate decreased obviously with the increase of salt stress concentration. (2) The net photosynthetic rate of peanut leaves increased with the increase of light intensity, but it would level off when the light intensity reached a certain value. The difference of light compensation point and light saturation point was great among different peanut varieties or salt concentrations. The high salt stress concentration increased the light compensation point of leaves, but decreased the light saturation point of saltsensitive cultivars. (3) The apparent quantum efficiency and maximum net photosynthetic rate decreased significantly with the increase of salt stress intensity. The ability of using weak light in saltsensitive varieties were stronger than that in salttolerant varieties under low salt stress. In the stress of 3.0 g/kg NaCl concentration, the maximum net photosynthetic rates of saltsensitive varieties were significantly lower than that of salttolerant varieties, while the apparent quantum efficiency of the two species leaves had similar drop among 78.65%-88.00%. (4) The free water content of salttolerant variety leaves was significantly higher than that of saltsensitive variety leaves in salt stress. In 2.0-3.0 g/kg NaCl stress, the fluctuation of SOD, CAT, POD activities and MDA content in salttolerant varieties were lower than that in saltsensitive varieties. The antioxidant capacity of salttolerant varieties was significantly higher than that of saltsensitive varieties when NaCl concentration was less than 2.0 g/kg. The study found the major reasons that plants could tolerant salt stress were the increase of light compensation point, maximum net photosynthetic rate, leaves preserve water ability, metabolism, antioxidant and osmotic regulation ability under salt stress.