Abstract: 【Objective】 Salt stress is one of the key abiotic stresses that cause yield loss and quality decline of tomato.Therefore, it is of great significance to reveal the molecular mechanism of tomato salt tolerance. 【Methods】 In this study, tomato salt-tolerant introduction system IL-7-5-5 and tomato salt-sensitive M82 were used as test materials, and isotope relative labeling and absolute quantification (TMT) technology were combined with quantitative parallel reaction monitoring (PRM) technology.The proteomics of leaves of tomato seedlings under 200 mM salt stress for 12 h were studied to screen out potential target proteins with significant salt stress response. 【Results】 (1)A total of 286 differentially expressed proteins (DEPs) were identified.Under salt stress, 191 DEPs were identified by IL-7-5-5, of which 119 were up-regulated and 72 down-regulated.157 DEPs were identified in M82, of which 84 were up-regulated and 73 down-regulated.Venn diagram analysis showed that 129 and 95 differential proteins were specific to IL-7-5-5 and M82, respectively.There were 62 differentially expressed proteins, among which 28 were up-regulated in IL-7-5-5 and M82, and 15 were down-regulated, showing consistent response to salt stress.Among the 19 differentially expressed proteins, 5 proteins were down-regulated in ST and up-regulated in SS, and 14 differentially expressed proteins were up-regulated in ST and down-regulated in SS; (2) The proteomic analysis showed that the GO enrichment tomato had strong salt reactive protein type induction ability, mainly related to metabolic process, single-tissue processes, and cellular processes and the cellular composition mainly involved cells, organelles, molecular compounds and membrane. And gene ontology revealed that these differential proteins were mainly involved in the regulation of catalytic activity, bound with molecular function,.(3) PRM validation results of 11 significantly different proteins showed the same trend as TMT quantitative results.Differential proteins included A0A3Q7E8T9, A0A3Q7EK65, A0A3Q7FY19, A0A3Q7G430, A0A3Q7ITH0, A0A3Q7J1Y7, P05116, Q43779, A0A3Q7F8W6,A0A3Q7GKU3 and A0A3Q7J0Z4, which might be potential target proteins for salt tolerance of tomato seedlings. 【Conclusion】 In this study, TMT combined with PRM technology was used to screen out differentially expressed proteins in tomato seedlings responding to salt stress, which could lay a foundation for further understanding of the molecular regulatory mechanism of tomato seedlings responding to salt stress.