Fishpass is one of the important methods to dam the river and block the migration of fish. In order to meet the requirements of upstream migration of fish after the construction of Xiajiang water conservancy project, protect the integrity of the Ganjiang River aquatic ecological environment and mitigate the effects of the project on the genetic exchange of fish populations, the way of fish passage was formulated according to the actual situation of Xiajiang water conservancy project. The fishpass, which was composed of upper fishpass (exit section), orifices of the dam, downstream main and secondary fishpass (entrance section), fish collection system and connection section, was designed using vertical joint structure. The designed main fish passage season was from April to July, and the flow velocity was 0.7-1.2 m/s. The effect of fish passing through Xiajiang fishpass was preliminarily monitored by means of instrument monitoring and manual observation. The results showed that a total of 678 000 fish were monitored from fishpass in 2017, of which the upstream fish accounted for 41.67%. There were 22 species observed, belonging to 4 orders, 7 families and 18 genera, mainly small species, such as Hemiculter bleekeri, Megalobrama terminalis, Xenocypris argentea and Squalidus argentatus. In different seasons, the number of fish was different, and the number in the second season accounting for 49.17% of all was more than that in other seasons; the number in July was more than that in other months. There is a big difference between night and day in the number of fish, with the largest number from AM 10:00 to PM 16:00. Compared with other fishpasses in China, Xiajiang fishpass has a large number of fish and a significant effect.