The glycerol dialkyl glycerol tetraethers （GDGTs） lipid composition was determined in surface sediments from the Eastern Lau Spreading Center （ELSC）, South Pacific Ocean. Isoprenoid and branched GDGTs were detected in all the samples. The relative contents of isoprenoid GDGTs were in the range of 58.1%-94.3% of total GDGTs. GDGT Ⅵ （crenarchaeol）, GDGT Ⅰ and GDGTV are the most abundant, suggesting significant contribution of archaea with the nonthermophilic crenachaea being the dominant strain. The isoprenoid GDGTs composition did not record the hydrothermal activities as high percentage of GDGTs was derived from nonthermophilic crenachaea. However, the branched GDGTs might record the hydrothermal activities. Relatively higher percentage （32.9%-41.9%） of branched GDGTs occurred in the samples taken from hydrothermal vent field, and relatively lower percentage （9.0%-16.7%） of branched GDGTs occurred in the samples taken from non-hydrothermal vent field. GDGT Ⅷa was the most abundant branched GDGTs in the samples taken from non-hydrothermal vent field. These patterns indicate that the branched GDGTs were derived from some anaerobic bacteria in situ, which supports the conclusion that branched GDGTs occurred not only in soils and peat bogs, but also hydrothermal vent field.%通过对南太平洋劳盆地东部扩张中（ELSC）表层沉积物样品中甘油二烷基甘油四醚脂类化合物（GDGTs）的分析结果表明，所有样品均检测出类异戊二烯GDGTs和支链GDGTs。其中，类异戊二烯GDGTs占总GDGTs的58．1％-93．4％，泉古菌醇（crenarchaeol）、GDGTⅠ和GDGTⅤ为其主要组分，说明古菌对于GDGTs的相对贡献量大，非嗜热泉古菌是最主要输入源，受其影响，热液活动记录难以从类异戊二烯GDGTs中识别。与此相比，支链GDGTs受热液活动影响明显。热液区样品的支链GDGTs占总GDGTs百分比普遍偏高（32．9％-41．9％），并表现出多种分布特征；而非热液地区样品中的支链GDGTs占总GDGTs百分比则较小（9．0％-16．7％），且均以GDGTⅧa为最主要的支链GDGTs化合物。这些分布特征表明支链GDGTs主要来源于原地厌氧细菌，这进一步拓宽了支链GDGTs的分布范围。
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