Objective: Taurine, the most abundant, semiessential, sulfur-containing amino acid, is well known to improve metabolic status in animal models. However, no rigorous clinical trial has validated whether this beneficial effect of taurine occurs in human, especially in prehypertensive participants. Design and Method: In this randomized, double-blind, placebo-controlled study, we assessed the effects of taurine intervention on metabolic parameters, such as blood pressure (BP) levels, carotid intima-media thickness (IMT), ankle brachial index (ABI)/toe brachial index (TBI), BMI and biochemical parameters in prehypertensive participants. We randomly assigned 120 eligible prehypertensive individuals to receive either taurine supplementation (1.6 g per day) or a placebo for 12 weeks. Then we further validated the results in spontaneously hypertensive rats (SHR), which were were intervented with 2% taurine water for 12 weeks. Results: Totally 97 participants completed the trial and no significant difference observed between the taurine and placebo groups. Taurine supplementation significantly decreased the clinic and 24-hour ambulatory BPs, especially in those with high-normal BP. In addition, taurine supplementation significantly improved endothelium-dependent and -independent vasodilation and reduced IMTs of these prehypertensive participants. Meanwhile taurine intervention increased plasma H2S and taurine concentrations. Other parameters did not change significantly upon taurine treatment compared with pre-treatment or placebo group. To further elucidate the mechanism, experimental studies were performed both in vivo and in vitro. The results showed that taurine treatment exerts hypotensive effects by upregulating the expressions of H2S-synthesizing enzymes and reducing agonist-induced vascular reactivity through the inhibition of TRPC3-mediated calcium influx in human and mouse mesenteric arteries. Also, taurine reduced ROS levels and improved mitochondrial respiratory fucntions in VSMCs from SHR compared with control group, thus inhibiting vascular remodeling pathways. Conclusions: Taurine supplementation improved vascular function of prehypertensive participants and SHRs by lowering BP levels and reducing IMT values. Taurine may become a new dietary factor improving the metabolic status in prehypertension.