Abstract: Combination of adding the exogenous NO donor sodium nitroprusside (SNP) with different concentrations, Isatis indigotica leaves were treated with 10% PEG 6 000 solution for 8 days to determine the effect of exogenous nitric oxide on oxidative damage fluorescence under drought stress. This study showed that exogenous NO treatment increased the accumulation of Proline and soluble sugar content of Isatis Indigotica leaves with the strengthening drought stress, and that the low concentrations of NO increased SOD and POD enzyme activity, while the high concentrations of NO restrained the activity of these two kinds of enzymes. This study also indicated that the variation of MDA contents of Isatis Indigotica leaves in same treatment showed a decreasing trend while low concentrations of NO made greater decreased in MDA content. The results of this study suggested that exogenous NO treatment increased the drought resistance of Isatis Indigotica.