Abstract: Guan-fu base A, a new antiarrhythmic alkaloid with a structure ofC₂₀-diterpenoid, was first isolated from the tuber of Aconitum coreanum (Levl.)Raipaicsin China in 1966. An analytical method of GC-ECD has been established in this paperfor the determination of its concentration in rabbit plasma in order to study its pharmacokinetics in preclinical pharmacology. Guan-fu base A and the internal standardalprenlol (ALP)was found to react rapidly and quantitatively with trifluoroacetic anhydride(TFAA)to produce derivatives GFA-TFAA and ALP-TFAA which were identified byGC-MSD. An optimal GC-ECD system for the separation and determination of thederivatives following the sample preparation was established. There was a wide linear rangeof the method from 10～2×10⁴ng/ml (r=0. 9984). The average recovery of Guan-fubase A from the spiked plasma was 97.52%. The coefficient of variation of between-dayand within-day were less than 9% and 7%, respectively. The method was used to determineGuan-fu base A in the plasma of 15 rabbits following intravenous administration of 3dosages of 0.4, 2 and 10 mg per kg of body weight.