Abstract: Taking ‘Zheza 205’ tomato as test material, the relative expression of SlRR gene, the content of antioxidant enzyme system, reactive oxygen species and osmoregulation substances in tomato seedling leaves were measured to explore whether exogenous melatonin could effectively induce tomato RR genes expression to alleviate the damage of salt and alkali stress on tomato.The results showed that compared with the control, the expression of Solyc05 g006420.2（SlRR4）,Solyc10 g079700.1（SlRR5）,Solyc03 g113720.2（SlRR6）,Solyc02 g071220.2（SlRR7）,Solyc01 g065540.2（SlRR8）,Solyc05 g054390.2（SlRR9）,Solyc04 g08050.2（SlRR10） and Solyc12 g010330.1（SlRR11） were significantly increased under salt and alkali treatments.The activities of superoxide dismutase（SOD）,peroxidase（POD）,ascorbate peroxidase（APX） and the content of H₂O₂,■,and Pro increased significantly.Compared with the single salt and alkali treatment, the expression of SlRR4 and SlRR5 and the activities of SOD,POD,APX and content of Pro were significantly increased after melatonin pretreated tomato seedlings, while the content of H₂O₂ and ■ were decreased significantly.Therefore, exogenous melatonin pretreatment can significantly induce the expression of SlRR genes to improve the activity of antioxidant enzymes, reduce the production of free radicals, increase the content of osmoregulation substances to maintain the osmotic balance of plants, thus alleviating the damage of salt and alkali stress on tomato.