Three new C-19 diterpene alkaloids, along with two known ones, were isolated from the roots of Aconitum brachypodum Diels. The structures of the new alkaloids were established as N-deethyl-3-Oacetylchasmaconitine (1), N-deethyl-3-O-acetylyunaconitine (2), and N-deethyl-3-O-acetyljesaconitine (3). Their structures were elucidated by extensive spectroscopic methods, including 1D (H-1, C-13) NMR and 2D NMR (H-1-H-1 COSY, TOCSY, ROESY, HSQC, and HMBC) experiments, as well as high-resolution electrospray ionization mass spectrometry (HR-ESI-MS).