极大螺旋藻培养液经浓缩，脱盐，醇沉得胞外粗多糖（ＥＰＩ）。ＥＰⅠ依次经ＤＥ－５２和ＳｅｐｈａｄｅｘＧ－１００纯化得纯品多糖（ＥＰⅡ）。经ＳｅｐｈａｄｅｘＧ－２００检测，ＥＰⅡ为均一组分，Ｍｒ６００００。薄层层析、气相层析、红外光谱分析表明，ＥＰⅡ是由Ｌ－岩藻糖，Ｄ－甘露糖，Ｄ－半乳糖，Ｄ－葡萄糖和葡萄糖醛酸组成的酸性杂多糖，糖苷键为β型。免疫调节活性试验表明，ＥＰⅡ有提高小鼠的ＮＫ细胞杀伤活力，促进ＩＬ－２产生及淋巴细胞和混合淋巴细胞转化功能。 The culture medium of Spirulina maxima was concentrated, desalted, and ethanol precipitated to extracellular polysaccharide (EPI). EPI was sequentially purified by DE-52 and Sephadex G-100 to obtain pure polysaccharide (EPII). As detected by Sephadex G-200, EPII is a homogeneous component, Mr60000. Thin layer chromatography, gas chromatography, and infrared spectroscopy showed that EPII is an acidic heteropolysaccharide consisting of L-fucose, D-mannose, D-galactose, D-glucose, and glucuronic acid. The glycosidic bond is β. type. The immunomodulatory activity test showed that EPII can increase the killing activity of NK cells in mice, promote the production of IL-2, and convert lymphocytes and mixed lymphocytes.