<p>The aim of this study is to optimize the parameters of the weir combined fishway through numerical simulation, in order to better meet the needs of the target fish population. Firstly, use the MIKE21 model to simulate the flow field of the fishway and analyze habitat suitability. Then, based on FLOW-3D simulation, the influence of key parameters such as longitudinal slope gradient, length of pool unit, direction of orifice arrangement, and opening rate on the hydraulic characteristics of the weir combined fishway was studied using the controlled variable method. The results showed that 9% longitudinal slope gradient, 7.0&#xa0;m pool chamber unit length, 0.3 rectangular orifice aperture ratio, and staggered orifice arrangement were the best parameter design for A weir combination orifice fishway. The fishway under this parameter design could balance hydraulic efficiency and eco-friendliness. Meanwhile, the flow rate and turbulence intensity satisfied the needs of target fish species.In conclusion, the study optimizes the parameters of A weir combination orifice fishway by numerical simulation. This provides helps to improve the ecological efficiency and engineering economy of the fishway.</p>