Abstract: Our research tentatively summarized the fragment pathways of three different types of diterpenoid alkaloids under electrospray positive mode and established a rapid method for identifying diterpenoid alkaloids in the roots of cultured Aconitum coreanum(Lèvl. )Rapaics. The powder of the roots was extracted with diethyl ether. After removing the diethyl ether under reduced pressure, the extract was dissolved in 0. 1% formic acid aqueous solution, separated on HPLC by using an Agilent Zorbax SB-C₁₈ reverse-phase column with a gradient elution of aqueous solution(containing 0. 2% formic acid, 0. 1% triethylamine)and acetonitrile, and then detected by Q-TOF mass spectrometer equipped with electrospray ionization source operated in positive ion mode. Compounds in the roots of Aconitum coreanum were identified by the accurate molecular weight obtained by HRMS, comparison of the MS fragment pathways and LC retention time with those of reference standards. As a result, 60 compounds were tentatively detected, 26 of which were assigned to known diterpenoid alkaloids. This established method is an accurate and effective way to identify the known constituents and discover the unknown ones from Aconitum coreanum.