Abstract: Cyanobacteria Toxins (Cyanotoxin, Mycrocystin, MC)were common in the eutrophic lakes of southern China. Using cyanotoxin as an indicator to find the higher pollution points in Tai Lake, China. From May to October, 1999,21points in Tai hu Lake were selected and detected 12 different indicators, including MC every month. The results of test were calculated means, standard deviation and correlation relations between indicators and districts. The stepwise regression was used to determine the relationship among all indicators. Dependent upon the established mathematical formula, using MC, total phosphorus and dissolve oxygen to find the main pollution points. Using ELISA test, the results of the geometrical mean of MC was 407 pgmL-1 (20.94 18362.02 pgmL-1). Through the stepwise regression method, the main influenced factors for concentration of MC were total phosphorus (positive correlation)and dissolved oxygen (negative correlation). The stepwise regression formula was as following: logMC=6.538+1.759*** log(total phospharus)-7.640* log(solved oxygen), (*P0.05, ***P0.0001).If conjugated with these three indicators we can find the main pollution points. Main pollution points in Tai hu Lake were located at points 16,24 and 9,10, in the bays of lake.