Objective To investigate the impact of adding folic acid and vitamin B12 combined with standard antihypertensive medication on plasma homocysteine (Hcy) and asymmetric dimethylarginine (ADMA),serum NO and endothelial nitric oxide synthase (eNOS) of essential hypertensive patients.Methods One hundred and fifty-six patients with essential hypertension were divided into control group and experimental group with 78 cases by random digits table method.Control group received conventional antihypertensive therapy,while experimental group were treated with folic acid and vitamin B12 based on the treatment of control group.Plasma Hcy and ADMA,serum NO and eNOS levels were observed at baseline 2 and 12 weeks after treatment.Results In control group,the level of Hcy and ADMA showed no significant difference before and 2,12 weeks after treatment (P ＞ 0.05).The level of Hcy and ADMA before treatment was significantly higher than that 2,12 weeks after treatment in experimental group (P＜ 0.05).The level of NO and eNOS 12 weeks after treatment in experimental group was significantly higher than that in control group[(77.35 ± 9.55)μmol/L vs.(64.26 ± 11.49) μ mol/L,(30.05 ±6.88) μ mol/L vs.(19.92 ± 10.24) μ mol/L,P ＜ 0.05].The level of ADMA was positively correlated with Hcy at baseline(r =0.612,P ＜ 0.05),and was negatively correlated with NO and eNOS (r =-0.557,-0.529,P ＜0.05).Conclusions Supplementation of folic acid and vitamin B12 helps to improve endothelial function and reduce plasma Hcy and ADMA levels as well as improve serum NO and eNOS levels in patients with essential hypertension,which helps to prevent from cardiovascular and cerebrovascular accidents.