Objective To investigate the influence of obstructive sleep apnea (OSAS) on circadian blood pressure variability and heart rate variability (HRV) in essential hypertensive patients. Methods A total of 91 patients admitted in our hospital were divided into three groups, according to the patients suffered from hypertension or/and OSAS, including normal group, pure hypertension group and hypertension complicated with OSAS group (complication group). The rate of non-dipper day-night blood pressure curve, time-domain indexes, frequency-domain indexes, average night blood oxygen level, apnea-hypopnea index (AHI) were compared among three groups. Results Compared with other groups, the rate of non-dipper day-night blood pressure curve, time-domain indexes, frequency-domain indexes, AHI were obviously higher in complication group (P＜0.01), and average night blood oxygen level were obviously lower in complication group (P＜0.01). Conclusion OSAS could make non-dipper day-night blood pressure curve, enhance HRV, descend average night blood oxygen level, and increase AHI, indicating that OSAS is an important risk factor to adverse cardiac events of essential hypertensive patients.