In total, 64 aquatic plant species were found in the investigation of 87 lake wetlands within the watershed of Lake Taihu in 2018, which belonged to 51genera and 33families. In general, the species richness, abundance and coverage of aquatic plants all decreased in research area compared to the historical data. This paper studied the taxonomic diversity and functional diversity of aquatic plants in four different (eastern, western, southern and northern) geographical regions. Results showed that the diversity index α was respectively 4.33, 5.58, 5.01 and 3.46 and the diversity index β was 3.46, 4.23, 1.63 and 7.02, respectively. Significant differences in taxonomic diversity α of aquatic plants were found between northern and western, northern and southern, eastern and western, eastern and southern, western and southern parts of the watershed. Meanwhile, taxonomic diversity β of aquatic plants was also significantly different between northern and eastern, northern and western, northern and southern, western and southern parts of the watershed. With respect to the functional diversity, the diversity index β of aquatic plants among four regions was respectively 0.18, 0.14, 0.09 and 0.30, which were significantly different in pairwise comparison. CCA results showed that the degree of explanation to the composition of aquatic plants in the lake wetlands with the environment variables was 21.21%, and the eutrophication might be one of the major issues leading the decline of aquatic plants.