Lake Hanfeng is located in the junction of east and south river in Kaixian county of Chongqing City in middle and upper reaches of Xiaojiang River in the Three Gorges Reservoir region.The change in its water level is dramatic (from 175 m when the Three Gorges Dam operated to 160 m in the summer) and mainly dually controlled by Three Gorges Reservoir and water level regulation dam of Lake Hanfeng in Wuyang village.The large fluctuation in water level has great influences on the quality of aquatic organisms including fish within the region but being rarly studied. This study analyzed the seasonal change characteristics of community structure of fish in the lake under the background of changing water level.The survey and analysis of community structure of fish in the Lake Hanfeng was carried out in Dec. 2014 and Apr., Jul., and Oct., 2015.A total of 8538 individuals were taxonomically identified, belonging to 38 species of 9 families in 5 orders. Among those, 28 species belong to Cypriniformes, accounting for 73.68% of the total,and mainly composed of limnicolous fish.The species number in each season was relatively stable, with 28, 28, 29, 33 species in spring,summer, autumn and winter, respectively.Pelteobagrus vachelli, Saurogobio dabryi, Squalidus argentatus, Carassius auratus, Pelteobagrus nitidus, Cyprinus carpio and Hemiculter bleekeri were the dominant species,accounting for 67.45% of the total.Seasonally,the number of dominant species was highest in winter (12),followed by spring (9),summer (11) and autumn (6).The fish diversity index, Shannon-Wiener index, Pielou evenness index and Margalef index was the highest in winter, while the lowest Shannon-Wiener diversity index and Pielous evenness index in summer.There were no significant differences between the seasonal Pielous evenness index and the Shannon-Wiener diversity index. Jaccard index was high,which indicated that more fish species overlapped seasonally.The Jaccard similarity index analysis showed that the similarity index of fish species in different seasons was higher than that in spring and autumn(83.87%). Fish community was stablest in winter, followed by spring, autumn and summer. The change in lake habitat, especially fluctuation of water level, had a significant impact on fish community structure in Lake Hanfeng.