Two new C-19-diterpenoid alkaloids, ducloudines A (1) and B (2), together with two known alkaloids of 14-acetylneoline (3) and aconitine (4), were isolated from the roots of Aconitum duclouxii Levl. The structures of new alkaloids were established on the basis of spectral data (HR-MS, X-ray crystallographic analysis, 1D- and 2D-NMR). Cytotoxicities of compounds 1 and 2 were tested against five cancer cell lines (HL-60, A549, SMMC-7721, MCF-7, SW480). Results showed that compounds 1 and 2 had no cytotoxic effects on these five tumor cells (IC50>40 μmol/L). © 2013 Chinese Chemical Society & SIOC, CAS.