Abstract: Fishway flow condition is an important factor affecting the fish passing effect. Based on the analyses of structural types and corresponding characteristics of the fishway, a partial hydraulic physical model with a large scale of 1∶ 4 is established for a vertical slot fishway, which is widely used in the water conservancy projects. The layout of the baffle and the vertical slot are studied under the conditions that a ratio of every pool’s length to width is less than 1.0. Three layout schemes are comparied in the experiments. Velocities of the vertical slot and velocity distribution, flow patterns and energy dissipation of the pool are tested and analysed. The baffle type is put forward suitable for the fishway with a small ratio of the pool’s length to width. Besides, the hydraulic characteristics are validated by an overall integral hydraulic physical model test which has a scale of 1∶12.5 when the fishway operates. The design rules are worked out to reduce local backwater of the baffles and enhance velocity uniformity of the vertical slots along the fishway. In order to suit the changes in water depth at the entrance and exit of the fishway, the studies of water supplement measures from an ecological open channel into the fishway are also carried out, showing that the minimum supplement discharge should be 0.22 m3/s. The test results show that the suggested baffle type can be applied to other similar fishway works.