Abstract: Community functional diversity is a bridge between species and ecosystem functions, which can effectively reflect the changes of ecosystem function. In this study, the catches in flood season (June, July, August) and dry season (November, December, January) in Peng’an section from 2014 to 2019 were investigated to analyze the functional diversity of fish community and its relationship with water environment using 11 fish functional traits. The main results are as follows: (1)The Species richness index, Simpson diversity index, Pielou evenness index and Shannon wiener index in the flood period of 2014—2019 were higher than those in the dry season; (2) Simper analysis showed that 10 species, Hemibagrus macropterus Bleeker, Rhinogobius giurinus Rutther, Pseudobrama simoni Bleeker, Pelteobagrus fulvidraco Richardson, Siniperca chuatsi Basilewsky, Saurogobio dabryi Bleeker, Pseudolaubuca sinensis Bleeker, Carassius auratus Linnaeus, Xenocypris davidi Bleeker, Hemiculter leucisculus Bleeker, were the main contributors to fish community structure during flood and dry seasons. (3) The functional richness (FRic), Functional divergence (FDiv), Functional Dispersion (FDis), Quadratic entropy (Rao) and Functional evenness (FEve) in 2015, 2016 and 2017 in flood season were significantly higher than those in dry season (P<0.05), indicating fragile aquatic ecosystem in dry season with low stability of resistance and resilience. (4) There was a significant correlation between the fish community functional diversity and the physical and chemical environmental factors. However, the correlation between functional diversity index and environmental factors in different periods was quite different, showing that the functional diversity was the result of the combination of fish community structure and water environmental factors.