OBJECTIVE To investigate effects of total flavonoid fraction of Asttragalus complanatus on blood pressure in conscious spontaneously hypertensive rats(SHR) and hemodynamics in anesthetized SHR. METHOD Blood pressure was recorded with tail-culf method and hemodynamics was recorded with polygraph after administration of total flavonoid fraction of Asttragalus complanatus. RESULT Total flavonoid fraction of Asttragalus complanatus (100, 200 mg.kg-1) could decrease blood pressure of conscious SHR(decreasing 7.1%, P < 0.05 and 9.3%, P < 0.01 respectively). Meanwhile, there was no significant change in heart rate(HR). R Br (200 mg.kg-1) could decrease total peripheral resistance (TPR) (decreasing 20%, P < 0.05) but did not influence the cardiac output(CO) and heart rate in anesthetized SHR. CONCLUSION Total flavonoid fraction of Asttragalus complanatus possesses obvious hypotensive effect, mainly by means of decreasing the TPR.