Abstract: Objective To investigate the characteristics of blood pressure variability and relationship between blood pressure circadian rhythm and age,gender in normotensives. Methods A total of 1024 out-patients who visited our clinic from January 2002 to December 2011 with normal blood pressure confirmed by 24 h-ambulatory blood pressure monitoring were enrolled in the study. The data of ambulatory blood pressure monitoring was collected and the standard deviations for 24 hblood pressure（24 hBPSD）,daytime blood pressure（dBPSD）,nighttime blood pressure（nBPSD）and 24 hblood pressure weighted standard deviation（24 hBPWSD）were analyzed. The standard deviation and coefficient of variation were used to represent the blood pressure variability. The nocturnal BP reduction rate was calculated by the formula:（daytime average systolic blood pressure-nighttime average systolic blood pressure）/daytime average systolic blood pressure.Patients were divided into anti-dipper,non-dipper,dipper and ultradipper group according to the nocturnal BP reduction rate and into ＜40,40-＜50,50-＜60 and ＞60 years old group according to the age. Results In normotensives,the percentages of anti-dipper,non-dipper,dipper and ultra-dipper were 6.0%,47.0%,43.6% and 3.4% respectively,and the standard deviations for 24 hsystolic blood pressure and for 24 hdiastolic blood pressure were（12.8±3.4）and（9.1±2.2）mm Hg,and the coefficient of variability of 24 hsystolic blood pressure and for 24 hdiastolic blood pressure were 0.11±0.03 and 0.13±0.03,respectively. 24 hBPSD,dBPSD and 24 hBPWSD in four groups（anti-dipper,non-dipper,dipper and ultra-dipper）increased along with the rising of nocturnal BP reduction rate and there was statistically significant difference（P＜0.05）in group pairwise comparison except for anti-dipper and non-dipper groups.While the difference was not statistically significant for nBPSD（P＞0.05）.24 h,diurnal and nocturnal systolic blood pressure standard deviation rose with the increasing of age（P＜0.05）,but the difference was not statistically significant for diastolic blood pressure standard deviation（P＞0.05）. Blood pressure variability in male group was higher than female group,but the difference was not statistically significant（P＞0.05）.Conclusion In normotensive population,blood pressure variability in anti-dipper and non-dipper groups were lower than dipper and ultra-dipper groups.Systolic blood pressure variability gradually increased with age but not gender in normal blood pressure population.