Abstract: The habitat suitability model for fish serves as a critical tool for assessing riverine ecological health. Current studies on habitat simulation for the Yellow River carp, an ecological indicator species in the Yellow River, predominantly rely on two-dimensional or three-dimensional hydrodynamic models. However, these approaches are often limited to short river reaches (tens of kilometers) due to high computational demands and challenges in acquiring high-resolution topographic data, with only water depth and flow velocity considered as influencing factors. This study develops a one-dimensional coupled hydro-sediment-thermal numerical model capable of accommodating arbitrary cross-sectional geometries and flow velocity distributions, enabling rapid simulation of flow-sediment-temperature processes across the entire lower Yellow River. Habitat suitability simulations based on daily-scale flow and sediment data from 1999 to 2021 reveal that total water volume is the dominant factor influencing downstream ecological health. The weighted usable area of habitats initially increases and then decreases with rising total water volume, peaking within an optimal range of 25.5~36.5 billion m3. At total water volumes of 20~25 billion m3, the significant dispersion of the weighted usable area highlights the dominant role of flow and sediment changes in shaping ecosystem health. Simulations further demonstrate that high sediment concentrations during flow-sediment regulation periods drastically reduce the weighted usable area. However, the overall impact of sediment remains limited due to the short duration of high-sediment processes during flood seasons. This study provides a foundational tool for assessing river ecosystem health and supports the exploration of ecological thresholds, offering insights for sustainable water resource management in large sediment-laden rivers.