To study the triterpenoid constituents from air-dried whole plants of Lycopodium obscurum L., the constituents were isolated by normal-phase and reverse-phase silica gel column chromatorgraphy from the EtOAc extract.  Their structures were elucidated on the basis of spectral analysis.  Five triterpenoids were  purified and identified as 3β, 19α-dihydroxy-20β-acetate-serrat-14-en-21β-ol (1), serratenediol (2), α-onocerin (3), 26-nor-8-oxo-α-onocerin (4), (3β, 8β, 14α, 21α)-26, 27-dinoronocerane-3, 8, 14, 21-tetrol (5).  Compound 1 is a new serratane-type triterpene and compound 5 is isolated from this plant for the first time.