In order to purify the eutrophic water, we setup a pilot system of the constructed wetland (CW) at the entrance of Xihu Lake, Hangzhou, China. The CW, consists of two plots A and B, is 18m long, 9m wide and 1.2m deep, and the sizes of both plot A and B are 9m long and 9m wide. The substratum of wetland were sands (diameter 1～3mm, 600mm depth) and gravel (diameter 30～50mm, 300mm depth) , on which Lolium perenne Linn was planted from winter to spring, and Coix lacryma jobi Linn. from summer to autumn...