Possible cardiotoxicity of ephedra to test animal was investigated in variation of pulse,myocardial enzyme spectrum,electrocardiogram and pathologic histology.Fifty-six rabbits were divided into 4 groups randomly with intra-gastric administration of 20.0 g/kg body weight(high dosage),10.0 g/kg body weight(middle dosage),2.0 g/kg body weight(low dosage) concentrated extracts of ephedra,and 10.0 g/kg body weight distilled water(CK)，respectively.Ephedrasolution was administrated for 7 d continually.Pulse(P) and electrocardiogram were measured pre and post ephedra treatment.Blood and myocardium tissues were sampled to assay myocardial enzyme spectrum.Pathologic changes of heart were observed post ephedra treatment.The results showed that pulse slowed down significantly in rabbits treated with high dosage and middle dosage of ephedra.Myocardial enzyme spectrum was in disorder expressed predominately by the significant increase of the enzyme activities.Cardiogram showed abnormality with enhanced amplitudes of P wave and R complex,and increased PR interval.Both high dosage and middle dosage prolonged/reduced QT interval.Damage occurred in myocardial tissue structure as well as the whole heart after ephedra treatment.The results indicated that ephedra affected the heart functions and damaged myocardial tissue structure apparently with dose dependent manner to a certain extent.