Abstract: In order to understand the status of fish resources in the dam site section of Wudongde Hydropower Station in the lower reaches of the Jinsha River before impoundment, a fish resource survey was conducted in dam site section from 2016 to 2018, and the composition and structural characteristics were analyzed. The results showed that a total of 59 fish species were collected in the section, belonging to 5 orders, 12 families and 41 genera, of which 17 species were endemic to the upper reaches of the Yangtze River, accounting for 28.81% of the collected species. The dominant species were Silurus meridionalis, Coreius guichenoti, Carassius auratus, Hemiculter tchangi, Pseudorasbora parva, Glyptothorax sinenses, which accounted for 67.42% of the catches. The Margalef richness index, Shannon-Weiner diversity index and Pielou evenness index were 7.28, 3.31 and 0.81, respectively. The survey results showed that the number of fish species in the dam site section before the damming had decreased compared with historical records, and the resource status showed a declining trend. However, the diversity of fish communities was higher, and the composition structure was relatively stable. In order to protect the fish biodiversity in the lower reaches of the Jinsha River, it is recommended to take measures such as habitat restoration, hydrological improvement and resource proliferation to create good living conditions for fish and maintain the natural population size.