Abstract: Objective To explore the relationship between nocturnal mean diastolic blood pressure and moderate-severe obstructive sleep apnea hyponea syndrome（OSAHS） in hypertensive patients and evaluate the value of nocturnal mean diastolic blood pressure in diagnosing moderate-severe OSAHS. Methods Clinical data of 144 hypertensives who underwent polysomnography（PSG）, ambulatory blood pressure monitoring（ABPM） in our hospital from September 2018 to November 2018 were recruited. Datas of STOP-Bang questionnaire, No-Apnea model and anthropometric measurements were collected,as well as NoSAS（neck, obesity, snoring, age, sex） score. According to apnea hypopnea index（AHI）, the patients were divided into non moderate-severe OSAHS group（AHI≤15 times/h, n=89） and moderate-severe OSAHS group（AHI＞15 times/h, n=55）. The receiver operating characteristics（ROC） curve was applied for evaluating the diagnostic value of nocturnal mean diastolic blood pressure and present tools for screening moderate-severe OSAHS. DeLong method was used to determine whether there was statistical differences among each indicators’ ROC curve. Sensitivity, specificity, positive predictive value, negative predictive value, Youden index, accuracy, Kappa value were also calculated for each indicator. Results There were 102 males and 42 females recruited with mean age of（45.4±11.1） years. When the cutoff point of AHI was 15 times/h, the AUC of nocturnal mean diastolic blood pressure was 0.725 with the best cutoff point as 86 mm Hg（Youden index 0.463）. Sensitivity, specificity, positive predictive value, negative predictive value of nocturnal mean diastolic blood pressure at the cutoff point were 63.2%, 83.1%, 70.0%, and 78.7%, respectively. The Youden index, accuracy and Kappa values were better than those of the present screening tools. After being connected to the No-Apnea model, the sensitivity, specificity, positive predictive value, negative predictive value, Yoden index, accuracy and Kappa value were 61.8%, 91.0%, 81.0%, 79.4%, 0.528, 79.8%, 0.553, respectively. All of the predictive indicators have been improved except for the sensitivity. Conclusion Nocturnal mean diastolic blood pressure with a good diagnostic value is closely related to moderate and severe OSAHS in hypertensive people. It can improve the diagnostic value of moderate-severe OSAHS after being connected to No-Apnea model.