Carbon dioxide partial pressures(pCO2 ) and CO2 fluxes on air-water interface in different trophic-level areas of Taihu Lake werecalculated and corrected using alkalinity, pH, ionic strength, active coefficient, water temperature and wind speed on the basis of the data setsof monthly sampling in 1998. The mean values of pCO2 in the hypertrophic, eutrophic, and mesotrophic areas are 1807.8 + 1025.8(mean +standard deviation) μatm, 416.3 + 207.8 μatm, and 448.5 + 194.0 μatm,respectively. A maximum and minimum pCO2 values were found inthe hypertrophic(4053.7 μatm) and the eutrophic(3.2 μatm) areas. There was about one magnitude order of difference in mean CO2 fluxesbetween the hypertrophic area(27.3 + 17.4 mmol/( m2 @ d) ) and the eutrophic ( 1.99 + 4.50 mmol/( m2 @ d) ) and mesotrophic ( 2.22 + 4.31mmol/( m2 @ d)) areas. But there was no significant difference between eutrophic and mesotrophic areas in pCO2 and the flux of CO2. In respectto CO2 equilibrium, input of the rivers will obviously influence inorganic carbon distribution in the riverine estuary. An exponential relationshipbetween the pCO2 values and chlorophyll-a concentrations was obtained( r ＝ 0.8356, n ＝ 60) in eutrophic bay. Results suggested that lakeecosystems, also may be considered as unique aggregation, which can contain and be patient of different components that have their relativeindependence so long as its size enough to large. A productive lake, though it has positive fluxes of CO2 to atmosphere during the most of time,is a huge and permanent sink of carbon in terrestrial ecosystems through receiving a great quantity of carbon materials via rivers, precipitation,and biological production.