A large amount of salt solution with special flavor could be recovered when the soy sauce was desalted by electrodialysis method. The effect of desalination on the migration of soy sauce components under different electrodialysis conditions was studied, and the composition of flavor substances in the salt solution was analyzed. The results showed that the effect of changes of electrodialysis voltage on the migration efficiency of NaCl in soy sauce was much greater than that of amino acid nitrogen (AAN) and total acid (TA). Under the conditions of electrodialysis voltage 13 V and treatment time 30 min, the loss rate of AAN and TA in soy sauce was low, and the removal rate of NaCl reached 41.97%, and the contents of NaCl, AAN, and TA in the salt solution were 6.60 g/100 ml, 0.135 g/100 ml, and 0.208 g/100 ml, respectively. The salt solution contained 15 kinds of free amino acids, mainly alanine, leucine and lysine, and the total free amino acid (FAA) content was 0.31%. Among them, the mobility of umami amino acids was lower, the mobility of sweet and bitter amino acids was higher. 17 kinds of flavor substances were detected in the salt solution, including phenylethanol, 3-methylthio propanol, 3-methyl-1-butanol, furfuryl alcohol, 4-ethyl guaiacol and other characteristic flavor substances of soy sauce.