Based on the historical data of fish catches and bottom trawl surveys on fish assemblage from 2014 to 2015 in Lake Hulun, the characteristics of fish community structure and dynamic variation of fishery resources were analyzed.The results showed that only 21 species (belonging to 21 genera, 6 families and 4 orders) were collected in Lake Hulun and Cypriniformes had the largest species number,accounting for 81.0% of the total species captured.The dominant species were Hemiculter bleekeri, Cultrichthys erythropterus, Cyprinus carpio, Carassius auratus gibelio and Leuciscus waleckii, and the Margalef richness index, Shannon-Wiener index and Pielou evenness index were low in Lake Hulun.In addition, the percentage of large fishes and the diversity indexes were found higher in the western lake region than those in the eastern lake region, whereas the number of fish species showed the reverse trend. Compared with historical data, we found that the composition of fish species and the dominant species had changed and the miniaturized tendency of fish resources was more obvious.Overfishing,lake eutrophication and changes of climatic and hydrological conditions are potential underlying reasons for observed shifts in the fish assemblage.