Remote sensing（RS） data can be used to estimate the chlorophyll-a concentration of water body

which has become a key issue of water quality monitoring.In this paper the field water reflectance spectra have been applied for monitoring the water quality of Taihu Lake according to reflectance spectra of water varying with concentrations of organic and inorganic sediments.After analyzing the spectra character we selected the optimal band range（670—710nm）

and retrieved the chlorophyll-a concentration by linear spectral unmixing model using known water and chlorophyll-a endmember spectra of in situ-water samples.TM and HEPERION image was processed and the distribution of chlorophyll-a concentration was retrieved by linear spectral unmixing method.The result shows that a fine linear correlation exists between the abundance of chlorophyll-a from the spectral unmixing model and the concentration of chlorophyll-a from the analytical result in the laboratory

and also shows that spectral unmxing model is a feasible model in the practical application for water quality monitoring.