Abstract: By spraying tomato leaves with reduced glutathione (GSH), oxidized glutathione (GSSG) and glutathione synthesis inhibitor (BSO), respectively, the effects of glutathionmediated redox state on leaf photosynthesis in tomato under NaCl stress were investigated. The results showed that the application of exogenous GSH significantly induced an increase in  reducing power level, increased the net photosynthetic rate (P_n), stomatal conductance (g_s), transpiration rate (T_r), as well as the maximum quantum yield of PSⅡ (F_v/F_m), actual photochemical efficiency of PSⅡ (Ф_PSⅡ), photochemical quenching coefficient (q_P) and nonphotochemical quenching coefficient (NPQ), and enhanced the Rubisco activity and expression levels of RbcL, RbcS and RCA genes in leaves of tomato seedlings under NaCl stress. These results suggested that GSH alleviated saltinduced oxidative stress by protecting PSⅡ from damage caused by excess energy, and improving the photochemical efficiency of PSⅡ and dark reaction activity of photosynthesis. Although spraying GSSG decreased the level of reducing power and further aggravated the damage and photoinhibition of the leaf photosynthetic apparatus, P_n was not affected in combined stressed (NaCl and GSSG) plants, which might be due to the upregulation of expression levels of RbcL and RbcS genes. The application of BSO had no significant effects on redox state, CO₂ conductivity capacity and PSⅡ photochemical efficiency in tomato leaves under NaCl stress. However, compared to salt singly stressed plants, BSO application increased P_n, likely due to the upregulation of Rubisco initial activity and RCA and RbcS expression levels.