Abstract: To understand the distribution of fish diversity and changes in resource after the operation of cascade hydropower stations in the middle reaches of Jinsha River, we conducted surveys at 34 sampling sites along its mainstream and tributaries in 2019, 2022, and 2023.A total of 4 193 fish specimens, weighing 375.42 kg, were collected, belonging to 68 species across 46 genera, 12 families and 4 orders.The current status of fish resources in the middle reaches of Jinsha River was discussed using methods such as species ecological type and dominance classification, diversity index evaluation, and community similarity analysis.The results showed that the dominant species were Schizothorax chongi, S. wangchiachii, S. prenanti, S. dolichonema, Pseudorasbora parva, Abbotina rivularis and Rhodeus sinensis.The fish resources in the mainstream were abundant with the diversity index ratings ranging from good to excellent across different sections.Except Shuiluo River, Heibaishui River and Yanggong River, the diversity index ratings for tributaries varied from poor to good.Cluster analysis divided the fish composition in the mainstream into four groups: Liyuan to Jinanqiao section, Longkaikou to Guanyinyan section, Jinsha section and Yinjiang section.The tributaries were divided into five groups, with noticeable differences in fish composition within each group.Compared with the historical data, the number of fish species collected was higher than that in 2007~2008.There was a decline in rheophilic fish species and an increase in introduced species.The spawning scale of drifting egg-laying fish species had diminished, spawning sites had shifted, and fish resource had declined.The reduction of lotic habitats due to the damming of cascade hydropower stations was the main factor affecting fish in the middle reaches of Jinsha River.To address the cumulative impact of hydropower cascades, recommendations were proposed from the perspective of holistic habitat conservation in the middle reaches of Jinsha River, including protecting fish habitats, optimizing fish stocking strategies, conducting ecological scheduling, and enhancing publicity and early warning systems for the hazards of introduced species.The results can supplement basic data and provide reference for fish resources conservation in the middle reaches of Jinsha River.