From the chemical investigation of a Formosan soft coral Lemnalia philippinensis, we had discovered seven new sesquiterpenoids, including three ylangene-type sesquiterpenoids lemnaphilins A-C ( 1-3 ), two eremophilane-type sesquiterpenoids lemnaphilins D-E ( 4-5 ), one neolemnane-type sesquiterpenoid lemnaphilin F (6), and one 4,5-cycloneolemnane-type sesquiterpenoid lemnaphinolide (7), along with eight known compounds, lemnalol(8) , 11,12-dihydroxy-6,10-eremopi -laiene (9),4(S*)-acetoxy,10(S*)-hydroxy,5-oxo,l(S*),12(S*)neolemna¡V2(Z), 8¡Vdiene (10), laevinone A (11), 2-oxolemnacarnol(12), lemnal-1(10)- ene-2,12-dione (13), 2,7 -nardosinoxanedione (14), elongatol B (15). The structures of these compounds were established by the detailed spectral analysis (IR, MS, 1D, 2D NMR) and by comparison of the spectral data with those of the related known compounds. The cytotoxicity of fifteen compounds (1¡V15) against with three cell lines, including HepG2 (human liver hepatocellular carninoma cells)¡BMDA-MB231(human breast cancer cells) and A549(human respiratory epithelial cells)was also determined. Only lemnaphilin A exhibited cytotoxicity, with IC50 values 15.99¡B16.31and 15.81 £gg/mL.