Wet vegetation performed different physiological actions under different pollution loads, thus inducing different purification effects on pollutants. Since water of various rivers, lakes and ponds are polluted at different extents and purification levels currently in China, a typical submerged vegetation, Vallisneria spiraslis L. is selected to study the purification effects on total nitrogen(TN) under different purification levels, which is widely distributed in rivers and lakes of Yangtz middle and down stream. The targets of this paper are to determine the nitrogen degradation impacts of Vallisneria spiraslis L., and nitrogen accumulation and distribution in leaf and root rules, and inorganic nitrogen conformation transformation characters under 7 nitrogen loads during 7 to 22 Sept., 2006. The 7 nitrogen loads are 1.0 mg/L, 5.0 mg/L, 10.0 mg/L, 20.0 mg/L, 40.0 mg/L, 60.0 mg/L and 80.0 mg/L. The experiment data show that Vallisneria spiraslis L. have significant effects on nitrogen purification while the TN concentration equal to and less than 60 mg/L, and the contribution principles of vegetation are similar among the 6 loads. Whereas, when the TN load bigger than 80.0 mg/L, Vallisneria spiraslis L. have no obvious contribution on nitrogen purification. Meanwhile, the nitrogen accumulation principles in the leaf and root of Vallisneria spiraslis L. is interrelated to the TN load. However, its distribution ratio in leaf to root is unrelated with TN load. Furthermore, the conformation of inorganic nitrogen transform characters changed with the TN load increasing. It is concluded that ammonia concentration decreased rapidly while the nitrogen load less than 20.0 mg/L, and the ammonia concentration ratio in the inorganic nitrogen increased remarkably with the nitrogen load increasing. Results indicate Vallisneria spiraslis L. have different purification contribution extents which can be benefit for nitrogen removal in different eutrophicated water and wet vegetation restoration.