A new C18 diterpenoid alkaloid, leucostonine(1), was isolated from the whole plant of Aconitum leucostomumVorosch., together with twelve known diterpenoid alkaloids.Their structures were elucidated on the basis of extensive spectroscopic analysis, including HR-ESI-MS, 1D NMR and 2D NMR spectra.12 compounds were tested for their antifeedant activity against larvae of Spodoptera exigua Hiibner.Anthranoyllycoctonine and avadharidine showed considerable potent antifeedant activity(EC50<1 mg/cm2), followed by N-acetylsepaconitine, finaconitine and N-deacetylappaconitine(EC50<2 mg/cm2). © 2017 Chinese Chemical Society & SIOC, CAS.