Three new Lycopodium alkaloids, huperzines S (1), T (2), and U (3), along with eight known compounds, were isolated from the total alkaloids of the whole plant of Huperzia serrata (Thunb) Trev. (Huperziaceae). Those novel alkaloids were identified as 2β,13β-epoxyalopecuridine (1), 5α-hydroxy-6-oxodihydrophlegmariurine A (2), and 2,3-dihydro-12-hydroxyhuperzine B (3), respectively, by means of spectral techniques including NMR studies.