The purpose of this study is to explore the application of constructed wetlands in water treatment and reuse, especially the efficiency of water purification through aquatic plants in urban wetland parks, and the process configuration and effect of tail water purification in sewage treatment plants. This paper presents a variety of purification mechanisms for constructed wetlands, including sedimentation, filtration, adsorption, ion exchange, etc. At the same time, the removal efficiency of different aquatic plants on water quality indicators was investigated, and the comprehensive benefits of constructed wetlands in urban ecological environments were discussed in combination with cases such as urban wetland parks and tailwater purification of sewage treatment plants. The research shows that the aquatic plants in the urban wetland park have a significant purification effect on the water quality index, and the reasonable design of the tailwater purification of the sewage treatment plant can effectively realize the IV water quality standard. As an efficient water treatment technology, constructed wetland plays an important role in the ecological and aesthetic integration of urban wetland parks and the water purification of sewage treatment plant tail water, which has a positive impact on promoting urban sustainable development.