The water level variation of some reservoirs in China is 15 meters or more, which brings great difficulties to the design of fishway outlet. Although the structure of fish lock operated on the navigation principle of ship lock is relatively simple in flow conditions and can better connect with the fluctuation of reservoir water level, it is not widely used because of the complex metal structure of fish lock high investment and certain problems in operation reliability.In view of this situation, a fish evicting grille with rotation as the degree of freedom is proposed in the study to replace the commonly used horizontal movement fish evicting grille. The main transmission devices are arranged in the dry area above the highest water level. In this way, it ensures the stable operation of fish evicting grille and avoids placing part of the transmission device underwater, which may cause the underwater transmission device to be easily damaged by silt and difficult to repair. At the same time, floating trash chest is arranged at the outlet of fish lock to further reduce the dredging frequency of fish evicting grille and other equipment without affecting the migration of fish. Through the optimization and improvement of the fish sluice, the operation reliability and maintenance convenience can be improved comprehensively.