To explore the role of periphyton in nutrient cycle in eutrophic shallow lake,the effect of the periphyton attached on Potamogeton crispus on nitrogen and phosphorus loads was examined in a mesocosm experiment conducted in controlled greenhouse.A gradient of ten nutrient concentrations (nitrogen concentrations from 3 to 12 mg/L and phosphorus concentrations from 0.1 to 1.0 mg/L) was established with NH₄Cl,NaNO₃,KH₂PO₄.The results showed that: The content of periphyton chlorophyll-a (Chl.a),organic matter,inorganic matter and total periphyton increased significantly with nitrogen and phosphorus loads increase.The content of periphyton Chl.a,organic matter,inorganic matter and total periphyton reached peak at T10 (TN 12 mg/L, TP 1.0 mg/L) with Chl.a 2.005-4.765 mg/g(DW) periphyton,organic matter 29.027-94.886 mg/g(DW) Potamogeton crispus, inorganic matter 176.881-397.750 mg/g(DW) Potamogeton crispus,and total periphyton 205.909-492.636 mg/g(DW) Potamogeton crispus,respectively.Periphyton Chl.a,organic matter,inorganic matter and total periphyton generally increased with time.Differences in periphyton Chl.a,organic matter,inorganic matter and total periphyton were significant among growth periods, and showed rapid growth period > stable period > decline period.Moreover,this trend occurred at all nutrient concentrations.The periphyton Chl.a,organic matter,inorganic matter and total periphyton of decline period were 1.046-1.826,1.046-1.638,1.029-1.858 and 1.106-1.717 times those of stable period,and were 2.324-4.059,2.323-3.640,2.101-3.792 and 2.280-3.584 times those of rapid growth period.The results above indicated that the periphyton of Potamogeton crispus and its decline were enhanced by elevated nitrogen and phosphorus loads.