Based on the survey data in 2003 and 2019, the diversity of wetland vascular plants in Jianhu Provincial Nature Reserve in Yunnan was studied. The wetland plants were determined according to the standards issued by the State Forestry Administration and the division of relevant literatures. The results showed that there were 129 species of wetland vascular plants belonging to 83 genera and 34 families in Jianhu wetland, which could be divided into 12 distribution types and 12 forms. The temperate species accounted for 75.19% of the total number of wetland vascular plants in the reserve; There were 13 species endemic to China, accounting for 10.08% of the total number of wetland vascular plants in the reserve, including 4 species endemic to Yunnan, accounting for 3.10% of the total number of vascular plants in the wetland reserve. According to the classification and statistics of life forms, 92 species of hygrophytes, 19 species of submerged plants, 9 species of emergent plants, 5 species of floating plants and 4 species of floating leaf plants were obtained. The wetland vegetation consisted of 5 vegetation subtypes, hygrophyte type, emergent plant type, floating plant type, floating leaf plant type and submerged plant type, and 17 formations, for example, Polygonum hydropiper, Oenanthe javanica and Carexbolting sp. formation and Polygonum hydropiper, Polygonum amphibium and Polygonum strindbergii formation. According to the species habits, morphological characteristics, habitats and sources in the field investigation, it is determined that there were 4 categories and 63 species of secondary vascular plants in Jianhu wetland, and the floristic secondary degree was 48.84%. There were 39 species of wetland vascular plants in Jianhu Lake and Lashihai in Northwest Yunnan, with a species similarity of 22.29%, and 18 species of wetland vascular plants in Chenghai in Central Yunnan Province, with a species similarity of 10.00%, with a higher similarity with Lashihai. The results show that the vascular plants in Jianhu wetland are characterized by high species richness, significant temperate components, extremely low endemic rate, complete life forms, diverse community types, high floristic secondary degree and obvious components in Northwest Yunnan. The main reasons for the diversity of wetland vascular plants in Jianhu Lake are the high altitude, north latitude and serious human impact on Jianhu Lake, which are directly related to the characteristics of Jianhu Lake, such as shallow water, fast water replacement, low pollution, gentle lake bed inclination, large bank curvature and thick sludge at the bottom.