Abstract: Effects of exogenous glycine betaine on some physiological indexes of soybean variety Zhechun NO. 3 seedlings under NaCl stress were studied. The photosynthetic pigments content， proline content， malondialdehyde accumulation (MDA)， soluble sugar content， relative electric conductivity and root activity of soybean seedlings were investigated. The results showed that exogenous betaine significantly increased the photosynthetic pigments and soluble sugar content， decreased proline and MDA accumulation， reduced the relative electric conductivity of soybean leaves， and enhanced root activity of soybean seedlings， which indicated that the application of exogenous betaine could enhance the photosynthetic activity of soybean leaves， improve the osmoregulatory ability of seedlings， alleviate the damages caused by NaCl stress， and then improve the salt tolerance ability of soybeans.

Key words: Key words： soybean, glycine betaine, NaCl, physiologicalchemical index