OBJECTIVE： To study the effect and mechanism of tandospirone citrate （TC） on blood pressure in spontaneously hypertensive rats （SHR）. METHODS： SHR were divided into model group， positive control group （Levamlodipine besylate tablets， 2.5 mg/kg）， TC high-dose， medium-dose， low-dose groups （TC capsules， 40， 20， 10 mg/kg）， 8 in each group. Other 8 normal rats were chosen as normal control group. The rats were intragastrically administrated medicines， once a day， for 28 d. Systolic blood pressure （SBP） before first administration and after 0.5， 1， 1.5， 2， 3， 4 h of administration in each group were measured， and SBP after 1 h of administration were measured once every 7 d. After last administration， nitric oxide （NO） content in serum， endothelin， renin， angiotensin Ⅱ （Ang Ⅱ） and norepinephrine （NE） contents in plasma were detected. RESULTS： In single administration， compared with model group， SBP in 0.5， 1 h in positive control group and TC groups after first administration were obviously decreased （P＜0.05 or P＜0.01）， then SBP were obviously decreased only in positive control group and TC high-dose group （P＜0.05 or P＜0.01）. In multiple administration， compared with model group， SBP in 7th， 14th， 28th day of administration in positive control group and TC high-dose， medium-dose groups were obviously decreased （P＜0.05 or P＜0.01）. Compared with model group， NO content in serum in positive control group， TC high-dose group were obviously increased； endothelin， renin， Ang Ⅱ and NE contents in plasma were obviously decreased （P＜0.05 or P＜0.01）. Compared with positive control group， NO content in serum in TC groups was obviously decreased； endothelin， renin， Ang Ⅱ and NE contents in plasma were obviously increased in TC medium-dose group （P＜0.05）. CONCLUSIONS： TC can obviously decrease the blood pressure of SHR. The mechanism may be associated with adjusting the balance of NO and endothelin， and decreasing renin， Ang Ⅱ and NE contents.