The organic extracts of Formosan soft coral Cladiella australis, collected along the coast of Kenting, Taiwan. Investigation on C. australis has led to the isolation of ten compounds 1-10, including six new compounds, australin A (1), australin B (2), australin C (3), australin D (4), (24S)-3£]-acetoxy-24-methylchloest-5-en-21-oic acid (6)¡Bcladiosulfone (10), and three compounds were first isolated from the natural sources, 5'-acetylthymidine (7), 2'-deoxy-3'-O-acetylthymidine (8), p-vinylbenzyl alcohol (9), and one know compounds (24S)-3£] -hydroxy-24-methylchloest-5-en-21-oic acid (5). Structures of these compounds were determined on the basis of spectroscopic evidences (including MS, IR, 1D and 2D NMR). Cytotoxicity of these compounds toward various cancer cell lines has also been determined.