Abstract: The experiment used three different kinds of substrates (the medium coarse sand, blast furnace slag and cinder) as materials, and also used three height 1.0 m, 1.2 m, 1.4 m to set up the text. In order to study the purifying function of the Pearl River's water about the constructed wetland system under the hydraulic with 42 cm/d. The results showed that the constructed wetland system had obvious purifying function of the Pearl River,s pollutant TN,TP,COD.The removal rate of TN,TP,COD could reach 56.16%,93.49%,86.96%, respectively. The removal rates of systems were improved obviously with the increasing thickness of substrates.