Abstract: The Nansihu Lake wetland is one of the largest freshwater lake wetlands in China; its eco-environment plays an important role in flood storage, climatic regulation, water conservation and purification, and maintenance of biological
diversity. Evaluating the impact of alien invasive plants on biodiversity and the effect of exotic plant invasions on ecosystem processes by surveying all ranges of the Nansihu Lake wetland is vital. Literature search and field investigation were used to study alien invasive plants in Nansihu Lake wetland. A comparison of the species composition of alien invasive plants in Nansihu Lake wetland and in Qingdao, Mt. Kunyu and Binzhou coastal areas showed 41 species of alien invasive plants belonging to 19 families and 35 genera in the Nansihu Lake wetland. The largest families were Compositae and Leguminosae. The proportion of alien invasive species originating from the tropic zone was close to that from temperate regions. The proportion of alien invasive plants caused by intentional introduction was 39%. The number of alien invasive plants in Qingdao, Mt. Kunyu and Binzhou was greater than that in the Nansihu Lake wetland. The number of species in the most developed region Qingdao was the greatest. In total, 35 species found in Qingdao were not found in the Nansihu Lake wetland. Five alien invasive species were specific to the Nansihu Lake wetland and showed the aquatic plant characteristics of exotic invasive plants in the Nansihu Lake wetland. Similarity analysis revealed consistent Jaccard and Sorenson indexes, with the Nansihu Lake wetland most similar to Binzhou, then Kunyu areas and least similar to the Qingdao area. Combined with regulation analysis of alien invasive plants in Nansihu Lake wetland, corresponding countermeasures are suggested.