Abstract: The removal ability to total nitrogen (TN) from polluted water in Caohai Lake byseven species submerged macrophytes including Potamogeton crispus,Vallisneria spiralis,Myriophyllum spicatum,Ceratophyllum demersum.Potamogeton pectinatus,Chara sp .,Edodea canadinsis were studied in this paper.Results show that each species has great ability to remove TN and total phosphorous (TP);during the 27d experiment period,the removal percentage to TN and TP is 80 31% and 89 82%,respectively;TN concentration in water declined in negative exponent form with the time continuing;within the given TN concentration range (2 68～16 667mg/L),The removal rate of each species increased with TN concentration increasing.Furthermore,the use of TN_{_t} and V-TN curves for restoration of aquatic macrophytes is discussed.