The temporal and spatial distribution patterns of chlorophyll-a and its correlation with the main environmental factors were analyzed according to the monthly investigation from January, 2007 to December, 2009 in Lake Qiandao where a large number of silver carp and bighead carp stocked.Results showed that the concentration of chlorophyll-a in sampling stations located in the upper reach riverine and transitional zones of the reservoir showed a significant seasonal variations with two concentration peaks oc-curred in spring and late summer or early fall,respectively.The concentrations of chlorophyll-a in upstream sites(in the riverine and transitional zones) were significantly higher than those of downstream sites.The chlorophyll-a during the warm season was usu-ally stratified with a concentration peak occurring at depths between 4m and 12m, occasionally at a depth of 20m.The result of cor-relation analysis showed a weak correlation between chlorophyll-a and NO₂-N,COD_Mn ,water temperature( WT) and silicate (SiO₃^2- ),while no significant correlations of the chlorophyll-a were found with other environmental factors,especially with the TP in the water.The regression equation between chlorophyll-a and the correlated environmental factors could be expressed through the multiple linear stepwise regressions as:Chl.a=0.114WT +2.120COD_Mn +17.157SiO₃^2--37.391 NO₂-N -1.946.