To explore the species composition and diversity characteristics of the existing fish in the middle reaches of the Sancha River， nine sampling sites were set up in the water area of the Qianzhong Water Control Project in the middle reaches of the Sancha River from the dry season and the flood season in 2022 and 2023. Three surveys were conducted on fish resources， and the current status of fish resources and species diversity in the water area were analyzed. The results showed that a total of 30 fish species were surveyed in the middle reaches of the Sancha River， belonging to 3 orders， 6 families， and 26 genera. Cypriniformes were the most abundant with 23 species， accounting for 76.67% of the total. There were 7 protected fish species and 2 exotic species. The dominant species were Hemiculter leucisculus， Aristichthys nobilis， Spinibarbus sinensis， and Carassius auratus. The fish diversity indices were Margalef's species richness index （D） at 3.96， Shannon-Wiener diversity index （H'） at 1.93， Pielou's evenness index （J′） at 0.57， and Simpson's dominance index （C） at 0.75. The β-diversity indices analysis showed that the β_c and β_r for the reservoir area and downstream water area of the Qianzhong Water Control Project Area were 8.0 and 15.8， respectively. The Jaccard similarity index （JSI） between the reservoir and downstream water areas was 0.47， indicating a moderate dissimilarity. The study suggests that there is a significant habitat difference between the reservoir area and downstream water area， with a certain differentiation in fish species. This study provides fundamental survey data for the conservation of fish diversity and scientific management in the Qianzhong Water Control Project Area.