Objective To assess the correlation between obstructive sleep apnea-hypopnea syndrome (OSAHS) and hypertension. Methods Such databases as MEDLINE (1950 to April 2011), EMbase (1989 to April 2011), VIP (1989 to April 2011), WANFANG (1977 to April 2011), CBM (1978 to April 2011) and CNKI (1979 to April 2011) were searched to collect literatures about the correlation between OSAHS and hypertension. The literatures in conference proceedings and some unpublicized articles were also retrieved. All cohort studies and case control studies were included. Two reviewers independently collected the data, assessed the quality, and conducted the Meta-analysis by using RevMan5.1 software. Results Among the total 11 studies involving 4 019 participants were included, 1 was prospective cohort study and the other 10 were case control studies. The results of Meta-analyses showed that: a) the OSAHS was correlated with hypertension (P=0.16, RR=2.52, 95%CI 2.21 to 2.87); and b) the correlation between OSAHS and hypertension was related with the different grades of OSHAS (P=0.83, RR=1.84, 95%CI 1.53 to 2.22). The more severe grade the OSAHS, the greater possibility the hypertension. Conclusion OSAHS is significantly related with hypertension, and they may be the mutual risk factor for each other. The correlation between OSAHS and hypertension may be related with different grades of OSAHS.