Three new lycopodine-type alkaloids, 4alpha-hydroxyanhydrolycodoline (1), 4alpha,6alpha-dihydroxyanhydrolycodoline (2), and 6-epi-8beta-acetoxylycoclavine (3), and an artifact, lycoposerramine G nitrate (4), along with seventeen related known compounds, were isolated from the club moss Lycopodium japonicum Thunb. ex Murray (Lycopodiaceae). Their structures were elucidated by extensive spectroscopic methods as well as X-ray analysis. Compounds 1-4 were evaluated for their acetylcholine esterase inhibitory activity.