Three new norditerpenoid alkaloids, transconitine A, B and C, together with the known alkaloids yunaconitine, crassicauline A, foresaconitine, talatisamine, 8-deacetylyunaconitine, geniconitine, indaconitine, forestine, 14-acetyltalatisamine and chasmanine were isolated from Aconitum transsectum Diels. The structures of the three new alkaloids were determined by NMR spectroscopy and that of transconitine A partial synthesis.