Mercury is liable to translate into hypertoxic alkyl mercury in aquatic environment.Many studies confirmed that reservoirs have the effect of mercury reactivity,new built reservoirs manifest the the phenomenon of abnormal higher methylmercury value in water and fishes,and the inundated sediments and plants are the important source of the increased methylmercury in fishes in reservoirs.Three Gorges Reservoir is the world spotlight reservoir which inundates large areas after impounding due to its special topography,whether it can increase the methylmercury bioaccumulation rate of water and aquatic organism and emerge the mercury reactivity of reservoir is an important subject that is worth probing into.Therefore,we choose the wild fishes in Three Gorges Reservoir as respondents,analysising the total mercury(THg)and methylmercury(MeHg)in different tissues or organs(such as gill,heart,muscle and swim bladder)of fishes every other month systematically,the results as follows: The range of the THg concentration in fishes muscles in Three Gorges Reservoir is 0.51~254.83 ng?g-1,the mean value is 51.26.±43.04 ng?g-1; The range of the MeHg concentration in muscles is 0.05~188.89 ng?g-1,the mean value is 20.56±27.84 ng?g-1;The range of the ratio of MeHg/THg in muscles is 2.65~96.84%,the mean value is 34.89±22.72%,the concentrations of THg and MeHg and the ratio of MeHg/THg are in the low levels compared with the rivers,lakes and reservoirs in China and overseas,and the concentrations of THg and MeHg are all lower than the food restricted standard of mercury(THg is 300 ng?g-1 and MeHg is 200 ng?g-1).The concentrations of THg and MeHg in different tissues or organs show higher value in muscles and hearts and lower value in swim bladders and gills.The concentrations of THg and MeHg,the ratio of MeHg/THg,the bioaccumulation factors of THg and MeHg in different tissues or organs perform an increase trend with the rising of trophic level.Moreover,the values of THg and MeHg in pelagic fishes are higher than the demersal fishes.According to the previous survey results of Three Gorges Reservoir before impounding,the concentrations of THg and organic mercury in our study are lower than the pre-impounding,hence,Three Gorges Reservoir dont act out the obvious effect of mercury reactivity after impounding.