Abstract: The objective of this study was to elucidate the role of exogenous sucrose in enhancing salt tolerance of “Cang 6001” (salt-tolerant) and “Shi 4185” (salt-sensitive) wheat (Triticum aestivum L.) cultivars. Root elongation, soluble sugar content, ROS (reactive oxygen species) level and antioxidant defense reaction were examined in wheat grown in nutrient solutions with/without NaCl (150 mmol·L^-1) and/or sucrose (80 mmol·L^-1). The salt treatment induced significant inhibitory effects on plant growth. Root elongation was obviously (P < 0.05) restrained by treatment with 150 mmol·L^-1 NaCl. Compared with “Cang 6001”, “Shi 4185” seedlings were inhibited more significantly. The inhibition effects were somehow weakened by exogenous sucrose application. Exogenous sucrose obviously increased total soluble sugar contents in both “Cang 6001” and “Shi 4185” wheat cultivars. The increment in soluble sugar content in “Cang 6001” was less than that in “Shi 4185”, while “Shi 4185” contained less soluble sugar than “Cang 6001” under no exogenous sucrose application. Results of H2DCFDA fluorescence probe and fluorescence staining tests showed that exogenous sucrose pretreatment effectively decreased ROS (reactive oxygen species) level and consequently maintaining cell membrane integrity and decreasing root-tip cell mortality. Exogenous sucrose pretreatment also enhanced leaf SOD (P < 0.05), APX (P < 0.05) and CAT (P > 0.05) activities in both cultivars. It was concluded that exogenous sucrose increased wheat seedling salt tolerance. Put together, the results suggested that sucrose-mediated salt toxicity alleviation depended mainly on sucrose-mediated antioxidant defense capacity and membrane integrity. This study was positively significant for further understanding of physiological mechanisms of exogenous substances that drove wheat response to salt stress and screening wheat cultivars for high salt tolerance.