Objective To observe clinical efficacy of modified Sini Tang treating hypertension of Yang deficiency type. Methods Totally 121 patients with hypertension belong to Yang deficiency type were randomly divided into control group of 61 cases and treatment group of 60 cases. The control group was given calcium antagonist（ 5 mg per tablet）

β-receptor blocker（ 5 mg per tablet） and angiotensin converting enzyme inhibitors（ 4 mg per tablet） or angiotensin Ⅱreceptor antagonist（ 100 mg per capsule）

once a day for 1 capsule. In the treatment group

based on the medication of the control group

added modified Sini Tang

1 dose per day

and both groups are continuously treated for 8 weeks. The authors observed the change of blood pressure in consulting room and 24 h ambulatory blood pressure（ 24 h average blood pressure

24 h blood pressure standard deviation） in the two groups before and after treatment and evaluated clinical efficacy. Results The TCM syndrome total effective rate was 86. 67% in the treatment group

and 59. 02% in the control group. The treatment group was superior to the control group（ P < 0. 05）.After treatment

both blood pressure in consulting room and 24 h average systolic of two groups significantly decreased（ P < 0. 01）. In the control group

24 h and nocturnal systolic pressure standard deviation significantly decreased after treatment（ P < 0. 05 or P < 0. 01）. In the treatment group

24 h diurnal and 24 h nocturnal systolic pressure standard deviation significantly decreased after treatment（ P < 0. 01）. The level of 24 h and 24 h nocturnal systolic pressure standard deviation in the treatment group after treatment was much lower than those in the control group（ P < 0. 05）.Conclusion Modified Sini Tang has obvious curative effect to treat hypertension belong to Yang deficiency type and can effectively improve blood pressure variability.