Objective: To assess the association between daytime sleepiness and hypertension among patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). Methods: A total of 1 958 patients from Sleep Medicine Center of West China Hospital between January 2015 and January 2016 were included in the study. All subjects underwent one night polysomnography (PSG) and Epworth sleep scale (ESS) was estimated. The patients were divided into non-OSAHS group[apnea-hypopnea index (AHI)<5/h]and OSAHS group (AHI≥5/h) based on PSG, and then OSAHS group was further divided into those with and without daytime sleepiness groups according to ESS score (the cut point of ESS was 14). The association between blood pressure and risk of suffering from hypertension among patients with different degree of daytime sleepiness was explored by binary logistic regression. Results: There were 1 580 men and 378 women among the included patients, the mean age was (44.3±11.6) years old and the mean body mass index (BMI) was (26.4±3.8) kg/m2. Among these patients, there were 267 non-OSAHS and 1 691 OSAHS patients (1 275 without daytime sleepiness and 416 with daytime sleepiness). The prevalence of hypertension was higher among OSAHS patients (53.9%vs 28.8%) than non-OSAHS group, and OSAHS patients had higher systolic blood pressure (SBP)[(126.3±0.4) vs (116.3±4.9) mmHg], diastolic blood pressure (DBP)[(82.4±0.3) vs (78.1±3.7) mmHg]and mean arterial pressure (MAP)[(97.0±0.3) vs (90.9±3.9) mmHg]than non-OSAHS group. And OSAHS with daytime sleepiness also had elevated DBP[(84.5±0.6) vs (81.7±0.3) mmHg]and MAP[(98.8±0.6) vs (96.5±0.3) mmHg]than those without sleepiness (all P<0.05). After controlling for age, sex, BMI, smoking, drinking, AHI and related sleep parameters, OSAHS combined with daytime sleepiness increased the odds of hypertension by 23% (OR=1.23, 95% CI: 1.01-1.65) compared to OSAHS without daytime sleepiness. Conclusion: The daytime sleepiness is an independent risk factor of hypertension in OSAHS patients.