Abstract: Objective To investigate the correlation between degree of obstructive sleep apnea hypopnea syndrome (OSAHS) and blood pressure variability and serum level of leptin. Methods A total of 118 patients with OSAHS were enrolled,and the sleep apnea hypopnea index (AHI) was measured by polysomnogram (PSG) examination.According to the AHI,they were divided into the mild group,the moderate group and the severe group;while 40 healthy persons were included as the control group.The 24 hours ambulatory blood pressure (ABP) and the serum level of leptin were tested by Enzyme-linked immunosorbent assay (ELISA). Results ①As the aspects of index of AHI and serum level of leptin,the control group,the mild group,the moderate group,and the severe group were all gradually increased with a statistically significant differences (P<0.05).②When compared with the control group,SBP_day and DBP_night levels of OSAHS groups'were higher than those of the control group,and the SBP_night level of the moderate group and the severe group were higher than those of the control group (P<0.05).As compared with the mild group,the SBP_day,SBP_night,DBP_night level of the moderate group and the severe group were higher than those of the mild group (P<0.05).As compared with the moderate group,the severe group's SBP_day and DBP_night were higher than those of the moderate group (P<0.05).③The degree of disease was positively correlated with index of AHI,serum level of leptin,level of SBP_day,SBP_night,and DBP_night,and there was a significant difference among these groups (P<0.05). Conclusion The severity degree of OSAHS is closely related to blood pressure variability and serum leptin,which provides a new way for the classification of patients with OSAHS,and it has guiding significance for the diagnosis and treatment of this disease.