Six cycloartanes were isolated from ethanol extract of marine green alga Cladophora fascicularis by column chromatography. Procedure of isolation and description of these compounds are given in this paper. The structures were elucidated as （1）. 24-hydroperoxycycloart-25- en-3β-ol; （2）. cycloart-25-en-3β 24-diol; （3）. 25-hydroperoxycycloart-23-en-3β-ol; （4）. cycloart-23-en-3β, 25-diol; （5）. cycloart-23, 25-dien-3β-ol; and （6）. cycloart-24-en-3β-ol by spectroscopic （MS, 1D and 2D NMR） data analysis. Cycloartane derivatives are widely distributed the alga. All these compounds that have been isolated alga for the first time. in terrestrial plants, but only few were obtained in from terrestrial plants, were found in the marine alga for the first time.
