Val-Glu-Pro(VEP) is an angiotensin Ⅰ-converting enzyme (ACE) inhibitory peptide derived from Spirulina platensis. The antihypertensive effect of VEP in spontaneously hypertensive rats (SHRs) was investigated in 24 h after one single dose and in one-week with one single dose per day. The expression regulation of VEP on major components of the renin-angiotensin system (RAS) in the kidney and serum of the SHRs was also explored with Real-Time PCR and enzyme-linked immunosorbent assay (ELISA). The results indicated that the least effective dose of VEP was 5 mg/kg and it exhibited a dose-dependent manner with increased dosages. The lowest weighted systolic blood pressure (WSBP) and weighted diastolic blood pressure (WDBP) occurred in 6 h and 4 h after administration, respectively. During the one-week experiment course, the WSBP of the VEP-treated group (10 mg/kg) was significantly lower than that of the negative control group from the 5th day. Furthermore, the VEP treatment significantly down-regulated the mRNA expression of renin, ACE, and the angiotensinⅡ(AngⅡ) type 1 (AT1) receptor, and up-regulated the mRNA expression of the AngⅡ type 2 (AT2) receptor in the kidney of the SHRs, suggesting that the antihypertensive effect of VEP might be related to its inhibition on the RAS and that it might be of great prospects in prevention and treatment of hypertension.