Abstract: To address the critical issue of low flow velocity in the Yanzhiba right-bank branch channel in Yichang on the Yangtze River during the dry season after the flow cutoff, which fails to meet the hydrodynamic requirements for the natural spawning experiment of Chinese sturgeon, this study focuses on the synergistic effect of topographic construction and open-channel diversion. A three-dimensional hydrodynamic model covering the experimental site and the Yanzhiba reach was developed to quantitatively reveal the spatiotemporal distribution patterns of the flow field in the experimental site, and to propose a fundamental hydrodynamic construction scheme that satisfies the spawning requirements of Chinese sturgeon under engineering constraints. The results indicate that the combined effect of the alternating "deep pool-shallow shoal" microhabitat structure created by topographic construction and the water introduced from the main channel via open-channel diversion effectively reshapes the flow field in the experimental site, establishing a composite hydrological habitat pattern characterized by “slow-flow refuging, rapid-flow schooling, and turbulent-flow fertilization”. Under the recommended scheme (bottom width 10 m, channel depth 4 m, designed diversion flow 18 m3/s), the open-channel diversion provides a large-area stable base flow field for the experimental site, the local flow velocity in the habitat reconstruction area can reach 0.3-0.6 m/s. On this basis, with the combined application of localized flow generation by flow?generating pumps and supplemental flow from reservoir ecological operation, the velocity in the experimental site during the spawning period could be further increased to 0.5-1.0 m/s, which provides critical hydrodynamic support for the successful natural spawning trial of Chinese sturgeon at Yanzhiba, Yichang in 2025. This study reveals the spatiotemporal distribution patterns and improvement effects of the flow field under the combined regulation of topographic construction and open-channel diversion, and proposes a flow construction technology scheme for Chinese sturgeon spawning grounds applicable to the Yanzhiba branch channel. The findings provide measured data, simulation support, and engineering references for the precise regulation of hydrodynamic conditions in alternative spawning grounds for rare aquatic organisms in the Yangtze River.