To solve the problem of low fish migration efficiency in fish passages,this study analyzes the effects of different pier cross-sectional shapes on hydraulic characteristics and fish migration potential through numerical simulation.The study uses six pier shapes,including traditional rectangular piers and five improved streamlined piers,and compares and analyzes their effects on flow velocity distribution and fish migration efficiency of the main channel of the fishway.Research results show that streamlined piers can significantly reduce the accumulation of floating debris in the fishway and reduce water flow resistance,thereby optimizing the flow rate of the main channel.Especially under the K1-shaped pier design,the maximum flow rate of the main channel is effectively reduced,making the migration success rate of most target fish species has increased to 97%.In contrast,the design of traditional rectangular piers results in higher flow velocity in the main channel,lower fish migration efficiency,and much lower migration success rate than the improved design.In urban areas,streamlined fish passages can play a better ecological role under limited space and resource conditions,providing technical support for urban river ecological restoration and biodiversity protection.