By monitoring 24 hours circadian rhythm and vaso-active substances changes, to observe the effect of acupuncturing Baihui(DU20) to Qianding(DU21) on primary hypertension and explore its mechanism of action. Methods: One hundred and twenty patients with primary hypertension of 1-2 level (low risk) were randomly divided to two groups. Control group with health education and lifestyle intervention, and treatment group with acupuncture Baihui to Qianding plus health education and lifestyle intervention. Before and after treatment, two groups were monitored by 24h ambulatory blood pressure, calculated daytime average systolic blood pressure, nighttime average systolic blood pressure, daytime average diastolic blood pressure, nighttime average diastolic blood pressure, peak ratio of systolic pressure and diastolic pressure, renin, aldosterone and angiotensin. Results: Observation on the 4th and 12th weeks, both the groups could reduce the daytime and nighttime average systolic blood pressure, diastolic blood pressure, and compared with before treatment, there was statistically significant (P<0.01). In the control group, to compare the results of 12th week with 4th week, there are no statistical significance (P>0.05); in the treatment group, when compared the results of 12th week with 4th week, there was statistical significance (P<0.05), and the long-term efficacy of the treatment group is better. Comparison of 4th week and 12th weeks between the two groups, the treatment group performed better than the control group (P<0.05). Before and after treatment, blood pressure peak ratio in the two groups have increased, and there were statistical difference (P<0.05), while diastolic Gu Feng ratio in the two groups were not statistically significant (P>0.05). Before and after treatment, aldosterone, angiotensin in the two groups were no significant difference (P>0.05), but the comparison of renin showed statistical significance (P<0.05). Conclusion: Acupuncture Baihui(DU20) to Qianding(DU21) therapy can significantly reduce the day and night average systolic blood pressure and diastolic blood pressure, which have a certain effect on the circadian rhythm of blood pressure and the reduction of renin.