Bellamya sp.snails are very common in Lake Taihu.The effects of snail(Bellamya sp.) on the growth of Hydrila verticillata Royle and Elodea nuttalli ST John and dissolved nutrition elements were examined in a laboratory.After a week of exposure of snail and aquatic plant in a experiment, increments of the per unit of Hydrilla verticillata Royle in three groups were :H :0.475 g, L :0.106 g, C :0.021 g and increments of the per unit of Elodea nuttalli ST John were H :0.704 g, L:0.663 g, C :0.478 g respectively.In addition, the change of length and node of Hydrilla verticillata Royle and Elodea nuttalli ST John with snail were higher than those without snail.It could be concluded that the increase of nutrition by snail in water could stimulate the growth of Hydrilla verticillata Royle and Elodea nuttalli ST John, because the metabolism of Bellamya sp.increased the nutrition of water and the primary productivity of aquatic plant were similar in three situations with the same experiment environment.