Based on continuous monitoring data from 2005 to 2007 in Lake Taihu.spatisa and tempoml series wem analyzed using cluster analysis and self-correlation method for chlorophyll-a and total inorganic phosphorus, total inorganic nitrogen, water temperature and other physical and chemical faetom of the aquatic environment.The current spatial-temporal characteristics of water quality in Lake Taihu and their relationship with algal bloom are summarized.The results revealed that the spatial distribution of water quality roughly dividedintoten groups, includingthree estuaries, fourbays, center lake, westem area and eastern area. The dedree of eutrophication in estuaries and the northern bys was significantly higher than other area. while nitrogen and phosphorus in estuaries were higher than those in northern bays because of external 80urce pollution. A significant correlation between chlorophyll-a and total inorganic nitrogen, ammonia nitrogen, water temperature was noted. The monthly average chlorophyll-a displayed that algal bloom occurred from April to October and Meiliang Bay, Gonghu Bay。Zhushan Bay had high coincidence, showing multiple peaks.