This paper examines the water depth variations of vertical slot fishways (VSFs) without central baffle. Three experimental models are built for the research. The results show that: the adjoining pools should have the same fore-and-aft elevation difference to prevent obvious fluctuation of water depth. Instead of being uniform along the fishway, the water depth is affected by upstream and downstream water levels. The fluctuations of the water levels exert an impact to over a dozen pools at the end of the fishway. The water line characteristics are different when the downstream water depth is greater or smaller than the normal conditions. Under the working condition of backwater, the water depth increases uniformly in pools in the backwater section; under the condition of drawdown, the depth falls faster in the pools closer to the end of the fishway. Two flow profiles are obtained from the VFS: the Ml and M2, which are analyzed by the Bakhmeteff-Chow method. These findings help enhance the understanding of the hydraulic design of the fishway, and improve efficiency of the VSFs.