The effects of seed soaking with 10^-11, 10^-10, 10^-9, 10^-8, 10^-7, 10^-6, and 10^-5 mol/L 2, 4-epibrassinolide (EBL) on the germination, growth, solute accumulation and antioxidant metabolism of tomato seeds under 0, 50, 100, 150, and 175 mmol/L NaCl stress for 7 days were studied to reveal the effect and mechanism of brassinosteroids on improving salt tolerance of crops. The results showed that 10^-9 mol/L EBL soaking seeds could significantly promote the germination of tomato seeds under comparative higher salt stress of NaCl concentration. Under all treatments, excessive high EBL concentrations (10^-6 and 10^-5 mol/L EBL) of soaking seeds showed inhibition effect on tomato seed germination. After seed germination under salt stress, seed soaking with a certain concentration of EBL could significantly increase the length of the seed radicle and hypocotyl, the fresh weight of seedlings and seed vigor index, among which 10^-9 mol/L EBL seed soaking treatment had the optimum promotion effect, while seed soaking treatments with excessive EBL concentration showed inhibition effect on them. Soaking seeds with 10^-9 mol/L EBL could decrease the content of O₂^·-, H₂O₂, malondialdehyde (MDA) and proline (Pro) in germinated seeds of tomato under both 150 mmol/L NaCl stress and non-salt stress. Soluble sugar (SS) and soluble protein (SP) in tomato seedlings were increased significantly under 150 mmol/L NaCl stress. The treatment of 10^-9 mol/L EBL significantly promoted the activities of superoxide dismutase (SOD) and peroxidase (POD) in tomato seedlings, especially under salt stress. In summary, EBL soaking in a certain concentration range can significantly promote the seed germination and its seedling formation, and the effect of soaking with 10^-9 mol/L EBL is the optimum treatment under salt stresses, mainly because the application of EBL can actively promote the transformation of substances in the germination of tomato seeds, increase the accumulation of solutes such as SS and SP, enhance the osmotic adjustment, and increase the activity of SOD and POD enzymes, and alleviate the oxidative stress in tomato seed germination caused by salinity.