This study investigated the molecular mechanism of exogenous nitric oxide (NO) in enhancing lupin"s tolerance to saline-alkaline stress. Saline-alkaline stress was simulated using a 100 mmol/L NaHCO? and Na?CO? (1:1 ratio) solution, with sodium nitroprusside (SNP) as the exogenous NO donor. The experiment included seven treatments: blank control, saline-alkaline stress control, and five SNP concentrations (50–250 μmol/L). Key physiological indicators (soluble sugar content, sucrose synthase, and sucrose phosphate synthase activity) were measured, and transcriptome sequencing was performed on saline-alkaline-stressed and SNP-treated (optimal concentration) groups.Results showed that exogenous NO improved lupin"s salinity tolerance by increasing osmolyte (soluble sugar) content and enhancing key sucrose-synthesizing enzyme activities. Transcriptome analysis revealed upregulation of genes encoding β-furanofructokinase, sucrose synthase, and β-glucosidase, while genes for GDP-mannose 4,6-dehydratase and aldolase were downregulated. These changes optimized sugar metabolism efficiency under stress. Additionally, NO-regulated transcription factors (bHLH, WRKY, ERF, MYB, bZIP) were implicated in stress tolerance. The findings provide insights for breeding lupin varieties adapted to saline-alkaline soils.