Abstract:From the roots of Aconitum sinomontanum Nakai, a folk drug in Yunnan, three chemical collstituents were isolated. Two of their are C19-diterpenoid alkaloids and were determined as ranaconitine (1 ) and lappaconitine (2 ), respectively, other one as lycaconitic acid monomethyl ester (3 ) by the data of IR, H NMR, 13C NMR and MS.