Abstract: ML7113 wheat seedling was used for test materials for the purpose of investigating the effects of exogenous nitric oxide on wheat seedling growth, reactive oxygen species and photosynthetic characteristic under UV-B stress. Sodium nitroprusside (SNP) was selected as an exogenous nitric oxide (NO) donor, and the seed of wheat was pre-soaked with 0.1 mmol/L SNP for 24 h. Under the UV-B stress conditions, there were four treatment groups including control group (CK), ultraviolet ray UV-B stress treatment group (B), UV-B and sodium nitroprosside composite treatment group (B+SNP) and sodium nitroprosside individual treatment group (SNP). 7 days sampling after treatment respectively was selected to measure soluble sugar, soluble protein, proline, MDA, O₂^-, H₂O₂, stomatal density, photosynthetic pigments and chlorophyll fluorescence parameters. The results showed that, NO donor SNP could significantly increase the plant height of wheat-seedling after UV-B stress and soluble sugar, soluble protein and proline contents in leaves increased by 19.69%, 15.25% and 41.36%. At the same time, stomatal density of leaf positive surface increased by 10.34%. SNP could make photosynthetic pigments contents (chlorophyll and carotenoid) improve by 12.43% and 5.99%, and SNP could significantly raise their chlorophyll fluorescence parameter Fv/Fm and Fv/F0 by 0.5% and 5.16% compared with CK. Meanwhile, SNP could respectively decrease the level of MDA and H₂O₂ by 27.30% and 74.92% compared with CK and O₂^- producing rate significantly reduced by 24.47% . Related physiological indexes material content increase was needed to response to the wheat seedling damage under UV-B stress. While appropriate concentration of exogenous NO (0.1 mmol/L) could alleviate wheat seedling damage effect under UV-B stress. Consequently, exogenous NO could enhance wheat stress adaptive capacity under UV-B stress.