Thirty-three　compounds　(1-33)　were　isolated　from　the　rhizomes　of　Osmunda　japonica.　Their　structures　were　elucidated　on　the　basis　of　spectral　analysis　and　identified　as　ent-kaurene　terpenoids　(1-3),　anthraquinones　(4-8),　flavonoids　(9-12),　steroids　(13-15),　and　other　compounds　(16-33).　Compound　1-14,　19-27　were　isolated　from　the　genus　osmunda　for　the　first　time.　Compound　28-29　were　isolated　from　the　plant　for　the　first　time.　Cytotoxicities　of　all　compounds　against　Hela,　HepG2　and　A549　cell　lines　were　measured　by　MTT　assay,　and　their　antioxidant　activities　were　determined　by　DPPH　and　ABTS　radical　scavenging　assays.　Compound　2　exhibited　potent　cytotoxicity　against　Hela,　HepG2　cell　lines　with　IC50　values　of　9.31　and　9.66　mu　M,　respectively.　Compound　9　showed　good　antioxidant　activity.　The　Trolox-equivalent　antioxidant　capacity　(TEAC)　value　was　0.95　mM　in　ABTS　assay,　and　the　IC50　value　was　18.63　mu　M　in　DPPH　assay.