Abstract: This paper reported the main study results of the protozoans at the Dongting Lake Outlet of the Changjiang River for a Period of three years.The species composition and seasonal distribution, dominant taxa, seasonal changes of total protozoan abundance were examined.Based on their food preferences, the identified protozoan species were classified to the functional-trophic groups.Additionally, the possible resources of the river protozoan species, characteristics of the protozoan species composition in the middle and upper reaches of the Changjiang River, as well as the indication values of both protozoan functional-trophic groups and the dominants in monitoring river water pollution were also discussed.