Objective：To explore the correlation between blood pressure variability（BPV）and vascular endothelial function induced by nocturnal hypoxia events in obstructive sleep apnea（OSA）patients. Methods：Between February 2022 and April 2023，a total of 131 moderate to severe OSA patients were studied from the departments of Sleep Medicine Centers in three different hospitals， including the Affiliated Huai’an No.1 People’s Hospital of Nanjing Medical University，etc. Continuous non-invasive blood pressure （BP）monitoring was performed simultaneously during polysomnography（PSG）to calculate BPV induced by hypoxic events，the gap between the peak value of systolio blood pressure（SBP）and the lowest SBP during a hypoxia event reflects the amplitude of BP fluctuation（ΔBP）；the number of times ΔBP≥10 mmHg per hour/oxygen desaturation index（ODI）indicates the percentage of hypoxia-induced BP fluctuation. Endothelial function was assessed by flow -mediated dilation（FMD），and patients were divided into normal endothelial function group（n=70）and endothelial dysfunction group（n=61）according to the FMD value. The study analyzed and compared the BPV parameters between the two groups，aiming to explore the factors associated with BPV. Results：There were no significant differences between the two groups of patients in age，sex distribution，body mass index，and OSA severity. Compared with the normal endothelial function group，the endothelial dysfunction group exhibited higher Bnocturnal systolic peak BP［（152.0±7.2） mmHg vs.（148.1±8.8）mmHg］，nocturnal diastolic peak BP［（89.8±5.7）mmHg vs.（87.5±6.6）mmHg］，ΔBP［（15.3±2.9）mmHg vs. （13.3±2.7）mmHg］，the percentage of BP fluctuation［（63.5±14.3）% vs.（44.8±10.7）%，all P < 0.05］，a n d endothelin-1［（50.7± 7.0）ng/L vs.（47.8 ± 8.5）ng/L，P < 0.05］. After adjusting the baseline data of patients，the line regression model showed that the nocturnal SBP peak，the percentage of BP fluctuation，and ΔBP were all positively correlated with FMD（all P < 0.05）. Conclusion：For moderate-to-severe OSA patients，the elevation of BPV induced by nocturnal hypoxia events is closely correlated to vascular endothelial dysfunction.