Abstract: 【Objective】 To study the effect of exogenous GSNO (exogenous NO donor) on alleviating NaCl stress of tomato. 【Methods】 In this study, tomato cultivar Zhongshu 4 was used as experimental material. Tomato Seedlings under NaCl stress (100 mmol/L) were treated with NG:0.5 mmol/L GSNO (S-nitrosoglutathione, NO donor), NP: 1 mmol/L cPTIO (NO scavenger), NGP: 0.5 mmol/L GSNO compound 1 mmol/L cPTIO; The effects of exogenous GSNO on the growth and salt tolerance of tomato seedlings under NaCl stress were studied. 【Results】 After applying GSNO, the growth of tomato seedlings was significantly improved under NaCl stress, the chlorophyll content increased, the chlorophyll fluorescence parameters returned to normal, and the Calvin cycle enzyme activity returned to normal level. 【Conclusion】 This study shows that exogenous GSNO can alleviate the adverse growth and photosynthetic effect of tomato seedlings under NaCl stress.