Integrated vertical flow constructed wetland (IVCW) is a new type of ecological wastewater treatment, and its internal hydrodynamic characteristics are crucial for the efficiency of pollutant removal. To enhance the hydrodynamic characteristics and pollutant removal efficiency of IVCWs, this study systematically investigated the influence mechanisms of substrate arrangement, layer thickness ratio, and hydraulic load on the internal flow field and hydrodynamic characteristics of the IVCW system using CFD technology. Based on these findings, an optimized IVCW system was proposed, and its pollutant removal performance was examined through field measurements. The results showed that the highest hydraulic efficiency within the system (λ = 0.835) was achieved when the substrate was arranged in descending order of resistance coefficient from top to bottom (medium, high, low), with a layer thickness ratio of 1:4:1 and a hydraulic load of 0.7 m/d. Compared to the control group, the optimized IVCW exhibited significantly higher average removal rates for COD (Chemical Oxygen Demand), TP (Total Phosphorus), and TN (Total Nitrogen).This study provides technical support for the improvement and application of the IVCW system and holds significant implications for ecological wastewater treatment.