Abstract: The barrier of the Three Gorges Dam resulted in fragmentation of fish habitats. In order to understand the connection between the three Gorges lock and the fish in the upper and lower reaches, study the fish passing ability of the three Gorges Lock, the changes of fish composition, diversity and community structure were analyzed in June 2009, February 2012, February 2017 and February 2018. During this survey, 39 species of fishes were captured，belonging to 6 orders，10 families and 32 genera. Among these fishes, 4 species were endemic to the upper reaches of the Yangtze River and 2 species were endemic to the Yangtze River (paddlefish and hybrid sturgeon). Four species of fish appear more frequently which were Hemiculter leucisculus, Hemiculter bleekeri, Parabramis pekinensis and Pelteobagrus vachelli. There were 23 species of fish may have the ability to pass through the lock, 9 species of which can pass through the lock smoothly or settle in the lock. Protosalanx hyalocranius and Neosalanx taihuensis with weak swimming ability were also distributed in the lock, which was speculated that early larva fish could also reach the downstream through the lock to achieve the purpose of resource exchange up and down. This study provided practical basis for the ecological function of ship lock and the construction of new passageway.