目的：对马尾藻科植物半叶马尾藻［Ｓａｒｇａｓｕｍｈｅｍｉｐｈｙｌｕｍ（Ｔｕｒｎ．）Ａｇ．］藻体的甾醇类成分进行研究。方法：利用真空液相层析、ＳｅｐｈａｄｅｘＬＨ２０层析和反复硅胶柱层析进行分离，根据甾醇的理化性质和光谱数据鉴定其结构。结果：得到５个甾醇类化合物，分别确定为岩藻甾醇（ＳＰⅠ）、２４氢过氧基２４乙烯基胆固醇（ＳＰⅡ），（２２Ｅ，２４Ｓ）２４甲基５α胆甾７，２２二烯３β，５，６β三醇（ＳＡⅢ），ｓａｒｉｎｇｏｓｔｅｒｏｌ（ＳＰⅣ）和麦角甾醇过氧化物（ｅｒｇｏｓｔｅｒｏｌｐｅｒｏｘｉｄｅ）（ＳＡⅥ）。结论：ＳＰⅡ，ＳＡⅢ和ＳＡⅥ为首次从褐藻类中发现 Objective: To investigate the effects of Sargasum hemiphylum (Turn.) Ag. ] Algae sterol components were studied. Methods: The constituents were isolated by vacuum liquid chromatography, Sephadex LH-20 chromatography and repeated silica gel column chromatography. Their structures were elucidated on the basis of physico-chemical properties and spectral data of sterols. Results: Five sterol compounds were obtained and identified as SPⅠ, 24hydroperoxy24vinylcholesterol (SPⅡ), (22E, 24S) 24methyl  5αcholestane  7,22  diene  3β, 5,6β  three alcohol (SA Ⅲ), saringosterol (SP Ⅳ) and ergosterol peroxide (ergosterolperoxide) (SA Ⅵ). Conclusion: SP Ⅱ, SA Ⅲ and SAⅥ were found from brown algae for the first time