Abstract: Benzyltetrahydropalmatine (BTHP) produced parallel shift of the cumulative dose-response curves for phenylephrine in rabbit aortic strips and rat anococcygeus muscles to the right. Their PA₂ values were found to be 5.8 and 5.86 respectively. In pithed rats, the dose-response curves of methoxamine and B-HT 920 were not altered by BTHP 5～10 mg/kg which could increase the diastolic pressure. However, the rise in DP was not blocked by yohimbine 1～2 mg/kg. In isolated spontaneously beating guinea pig atria, the positive chronotropic action of both Iso and His can be antagonized by BTHP in a non-competitive manner. The pD₂' value for Iso was shown to be 4. In addition, the arrhythmia induced by reperfusion in rats was also antagonized by BTHP 5mg/kg.These results suggest that the blocking action of BTHP on α₁-and β-adrenoceptors and H₂-receptor are probably partially associated with its antiarrhythmic.