This paper studied the depuration effect of two kinds of submerged macrophytes Vallisneria spiralis and Elodea Canadensis in winter, after cold acclimation in laboratory. From 5 to 25 November 2009, ten large embankment enclosures were set up in Dong Jing River of the water source area in Gong Hu, Suzhou Vallisneria spiralis and Elodea Canadensis were planted in the enclosures. Experiments were made in 4 groups: Vallisneria spiralis, Elodea Canadensis, Vallisneria spiralis + Elodea Canadensis and control group. Each treatment had three replicates. Sampled once every five days, to test the water quality inside of the enclosure and the outside enclosure. The results showed that: (1) In the enclosures grown submerged macrophytes: concentrations of NH₄-N, NO₃-N, TN,were significantly lower than those before the experiment (P<0.01), and the concentrations in Vallisneria spiralis control, Elodea Canadensis control, Vallisneria spiralis + Elodea Canadensis control are reduced to 78.76%,70.20%, 83.42%,81.85%,72.30%,75.55%,88,80%,78.80%,86.21%, respectively ,while the control group and the water outside the enclosures have a lesser extent nitrogen concentrations, in which TN concentrations decreased 37.12% and 15.87%; (2)The control of Vallisneria spiralis + Elodea Canadensis have high reduction rate in decreasing the TP and COD_Mn, which were 86.97% and 76.16%, significantly higher than other controls(P<0.05). (3) The effect of purifying water of Vallisneria spiralis and Elodea Canadensis is better in winter, and the purifying effect: Vallisneria spiralis + Elodea Canadensis>Vallisneria spiralis >Elodea Canadensis. This paper provides a theoretical basis for the recovery of submerged plants of lake ecological restoration, species selection and reasonable allocation.