The absorption coefficient of water color constituents is an inherent optical parameter. It is the main factor which influences the distribution of the water optical field

and plays a very important role in the researches of water optics remote sensing. This paper analyses the absorption coefficient characteristics for particle matter

phytoplankton and colored dissolved organic matter（CDOM）

using the absorption coefficient of water color constituents in situ measured at the Three Gorges Dam in April

2007. The results show that

for the Three Gorges Dam water: （1） the absorption spectrum of non-algal particles is similar with that of total particle matter; （2） the absorption coefficient of non-algal particles decreases power exponentially from short to long wavelength

and the absorption coefficient in different bands has a definite relationship; （3） the absorption coefficient of phytoplankton has a better polynomial relationship with chlorophyll a concentration in the Three Gorges Dam water; （4） piece- wise function can express the absorption coefficient characteristics of CDOM. The absorption spectrum below 500nm decreases power exponentially from short to long wavelength

and the precision of the fitting R2approaches to 1; the absorption spectrum between 501 and 700nm fits well using polynomial relationship

and the precision R2 is above 95%.