Abstract: OBJECTIVE To observe the hypotensive effect of fresh Dendrobium officinale on spontaneously hypertensive(SH) rats and explore the potential mechanism. METHODS Twenty-four SH rats were randomly divided into three groups:fresh Dendrobium officinale group(0.8 g·kg^-1), amlodipine besylate tablet(Luohuoxi) group (0.5 mg·kg^-1) and model group. In addition, a normal control group was set up. Blood pressure was measured 3 times before administration and one time a week of 2 h after administration. After 8 weeks of treatment, plasma levels of angiotensin Ⅰ(Ang Ⅰ), angiotensin Ⅱ(Ang Ⅱ), renin activity(RA) and aldosterone(ALD) were measured. The mRNA expression of angiotensin Ⅱ receptor type 1(AT1R) and endothelin-1 in renal tissue was detected by RT-qPCR. RESULTS Compared with the model group, the systolic and diastolic blood pressures of fresh Dendrobium officinale and Luohuoxi groups decreased significantly at each time point of administration (P<0.05); the systolic and diastolic blood pressures of fresh Dendrobium officinale group and Luohuoxi group had significant difference only at one week after administration(P<0.05), but there was no significant difference at other time points. Compared with the model group, the level of AT1R mRNA in fresh Dendrobium officinale group and Luohuoxi group decreased significantly(P<0.05), but there was no significant difference between the two groups. There were no significant changes in plasma Ang Ⅰ, Ang Ⅱ, RA and ALD between fresh Dendrobium officinale group and Luohuoxi group. CONCLUSION Fresh Dendrobium officinale can significantly reduce the level of blood pressure in SH rats, and its antihypertensive effect is similar to that of Luohuoxi. It may play a role by reducing the level of AT1R mRNA.