The aim of this paper is to study the polysaccharide of the native water-bloom cyanobacterium Microcystisspp. and its effect on chemical and ecological properties of aquatic environments.Polysaccharides from the water-bloom cyanobacterium Microcystis spp. of Lake Dianchi were extracted with deionized water, pH5 and pH9.2 bufferat 4*C and 80*C.Partial chemical charactristics of extracted polysaccharides was investigated. The results showedthat pH 9.2 buffer got the highest yield that was 2.25%.The lowest yield was 0. 383% with pH5 buffer. The solubility test indicated that polysaccharides extracted by various methods were insoluble, partly solubilized or dispersedin the examined solvents.The monosaccharide composition analysis with GC and GC-MS indicated the extracted polysaccharides contained rhamnose, arabinose, mannose, galactose, glucose and one unknown sugar. The sulfuricacid carbazole method showed the presentation of uronic acid in the extracted polysaccharides.The metal contentwas determined with inductively coupled plasma quantometer. The polysaccharide extracted with deionized water at4*C was found to contain high concentration of Ca and Mg, which was 2.15% and 0.4%,respectively. Preliminary study indicated that the polysaccharide from Microcystis spp.was acidic heterogeneous polysaccharides. The lowsolubility of the polysaccharide showed it may form transparent exopolymer panicles easily in natural water. Thehigh metal-binding capability of the polysaccharide showed it may influence the solubilization,precipitation, bioavailability, and cycling of metals in aquatic environments, especially Ca and Mg.