Abstract: This study developed an LC-MS/MS method for the simultaneous determination and plasma pharmacokinetic study of berberine,jatrorrhizine and palmatine in beagle dogs after oral administration of Ermiao Wan.Six dogs (3 males and 3 females) were orally administered with Ermiao wan (equal to berberine 25mg/kg).Blood samples were collected into heparinized tubes from 0 to 48 h.The detection was performed by positive electrospray ionization (ESI) in the selected reaction monitoring mode.The main pharmacokinetic parameters of berberine,jatrorrhizine and palmatine were obtained as follows:c_max(4.474±1.8),(0.508 3±0.2) and (0.812 4±0.7) ng/mL,t_1/2(38.1±15.4),(23.8±9.9) and (20.2±17.1) h,AUC_{0-48 h}(37.4±3.9),(3.75±1.2) and (3.01±0.9) ng·h/mL.The results indicated that the oral bioavailability of berberine,jatrorrhizine and palmatine were very low.They were absorbed rapidly,and eliminated slowly in vivo.