Abstract: The seedlings of Hibiscus syriacus Linn.were used as materials,the effects of exogenous H₂O₂ on physiological indexes of Hibiscus syriacus Linn.under double salt stress were studied by pot experiment,in order to find a new way to improve its salt tolerance and to provide a theoretical basis.The results showed that T4 compared with T2 was significantly reduced the contents of Hibiscus syriacus Linn.superoxide anion,hydrogen peroxide and MDA content,and it was significantly reduced the conductivity,there was significant difference between T2 and control,but no significant difference between T6 and control;T4 compared with T2 that increased the content of AsA and GSH,there was significant difference between T2 and T1;T4 compared with T2 that significantly increased the activity of SOD,CAT and APX in Hibiscus syriacus Linn.,T2 was significantly higher than the control,and there was no significant difference between T6 and the control;T4 compared with T2 that increased the content of soluble sugar,soluble protein and free proline content in Hibiscus syriacus Linn.,T2 was significantly higher than the control;T4 compared with T2 that increases chlorophyll a content and chlorophyll a/b value,while decreases chlorophyll b and total chlorophyll content.According to the comprehensive analysis,T4 had the most significant effect on improving the physiological characteristics of Hibiscus syriacus Linn.under double salt stress and alleviating double salt stress.