Phlegmariurine B (1), a known alkaloid, along with three new analogous compounds, 2alpha-hydroxyphlegmariurine B (2), 2-oxoyphlegmariurine B (3) and 11-oxophlegmariurine B (4), were isolated from the CHCl3 fraction of total alkaloids of whole plant of the Chinese medicinal herb Huperzia serrata. Their structures were elucidated by spectral analysis.