Abstract: The correlation between the related enzymes activities of sucrose metabolism ( invertase, sucrose synthase, sucrose phosphate synthase) and sugar composition (sucrose, glucose, fructose) and content of tomato (Lycopersicon esculentu) were determined and analyzed under different concentration of salt stress. The results indicated that fructose and glucose content were increased under salt stress to a certain degree in tomato seedlings, but sucrose content was reduced. Invertase activities were enhanced in a short period of time, and also elevated expression of soluble acid invertase mRNA in tomato seedlings under salt stress, moreover. Sucrose synthase and sucrose phosphate synthase were reduced under salt stress, but compared no significant difference with control. It was suggested that the level of tomato seedlings sucrose metabolism were mainly modulated by gene expression and activities of acid invertase under salt stress.