Abstract: Fishway is an ecological passage that allows fishes to pass over the dam or do migratory swimming, and studies on the coordination of its flow and fish migration characteristics are an issue that attracts great attention recently. In this work, we examined the characteristics of flows in a fishway with a vertical slot and orifice plates and analyzed their effects on fish migration, using the k-ε (RNG) turbulence model and VOF model of the Fluent code through a case study of the Changzhou fishway. The results show that under the design flow condition (Q = 6.64 m3/s) of this project, the fishway flow can develop vertical profiles of velocity and turbulent kinetic energy that have little effect on the migration of Chinese sturgeon, shad, and other major fish species, while it will produce a greater obstacle to the migration of the Four Major Chinese Fish species of relatively low swimming ability. However, the inflow of the fishway is linearly proportional to flow velocities inside its chamber, and its hydraulic characteristics will basically meet the migratory needs of all the aforementioned major species if it is operated under a flow rate in the range of 3.64-4.64 m3/s. Thus, this study would be useful for optimizing fishway design and operation.