This research was carried on in Hei Tu Wa of Guan-Ting Reservoir in Yongding River upstream From 2004 to 2005. The phytoplankon communit was composed of 8 divisions (94 species，including genus and varieties) and the average cell density was 980.93×104 cells per liter. The dominant divisions were Chlorophyta (36.8%),Bacillariophyta (310%) and Cyanophyta (23.4%). The removal efficiency of phytoplankton density was 72.7%. There was a positive linear correlation between phytoplankon density and total phosphorous. Here,7 families (13 species) of aquatic vasular plants were found and constituted emerging and submersed macrophyte communities. In the wetland system, the zooplankton community consisted of Protozoa, Rotifera, Cladocera and Copepoda （70 species）. Their average density was 4883 individual per liter. Protozoan and Rotifera were the dominant groups and the removal efficiency of their density was 81.9 %. The correlation between zooplankton and phytoplankton presented quadratic curve. Also, the zoobenthos community contained Olisochaeta, Uniramia, Crustacea and Mollusca (15 species). Their average density was 5670 individual per m2 (62.3% was Uniramia) and the removal efficiency of their density was 92.4 %. The constructed wetland system reduced CODMn, BOD5,TN, NH3-N, NO3-N, TP, PO4-P and SS in the water of Yong Ding River at 52.9%-99.1%.