In order to understand the adaptability of plants in the wetland ecological island, the suitable plants, and the suitable type of ecological island, the overwintering situation of aquatic plants, ecological adaptability, and nitrogen and phosphorus accumulation were discussed by constructing two types of wetland ecological island in Wangshan River of Kunshan City. Results show that the overwintering germination rates of five chosen aquatic plants from high to low are: Iris sibirica, Iris pseudacorus, Pontederia cordata, Scirpus tabernaemontani, and Typha orientalis. The ecological island of gravel-soil matrix is conducive to the increase of the plants height and root numbers, growth of plants, and nitrogen and phosphorus accumulation, which will improve the ability of nitrogen and phosphorus removal of the wetland system. The plant adaptability and purification potential of four chosen aquatic plants from large to small are: Pontederia cordata, Iris sibirica, Iris pseudacorus, Scirpus tabernaemontani. Iris sibirica and Iris pseudacorus can be evergreen winter in the experimental region, which are suitable for urban river regulation in winter and the landscape effect is good.