Community structure and diversity of fish exhibit a strong correlation with environmental variables. We studied the spatial and temporal patterns of the fish community structure and diversity in both the small and main lake regions of Lake Hengshui throughout 2021. The relationships between fish community structure and environmental factors were analyzed. A total of 29 fish species across 15 families and 27 genera were recorded in Lake Hengshui. Cyprinid species contributed 98% to the total catch by weight. The dominant fish species in Lake Hengshui were Hemiculter leucisculus, Carassius carassius, Hypophthalmus molitrix and Pseudobrama simoni. There were no seasonal and spatial variations in Shannon-Wiener diversity index, Pielou's evenness index and Margalef's species richness index of fishes in the main region of the lake. However, permutational multivariate analysis highlighted significant temporal variations in fish community structure in the main lake region. Similarity percentage analysis revealed an average seasonal difference over 40% in fish communities of the main lake, the spatial difference of fish community structure between the main lake and small lake regions was 41%. The abundance-biomass curve indicated that fish communities in the main lake region was largely disturbed in all sampling seasons. In the small lake region, these disturbances were only observed in spring and summer, while not in autumn. Redundancy analysis indicated that the epilimnetic total phosphorus of the main lake explained most of fish community changes (36%). Total phosphorus, nitrite, secchi depth and total nitrogen were also the main contributors which influencing the fish community structure of the main lake. The fish community structure of Lake Hengshui is dominated by small omnivorous fish, such as H. leucisculus, C. carassius and P. simoni, while the abundance of piscivorous fish is relatively low. Therefore, in the context of enhancing water quality and ecological restoration, after the reduction of external nutrient loads, it is important to manipulate the fish community structure of Lake Hengshui. This involves strengthening the top-down effect by carnivorous fish, mitigating the potential adverse impacts of omnivorous fish and planktivorous fish on water quality, ultimately working towards the objective of improving water quality.