To address the issues such as dense structure, susceptibility to compaction, low organic matter, and nutrient deficiency in the dredged alluvial soils within the Yellow River basin, and to enhance their potential for resource utilization and vegetation restoration, five types of organic and inorganic soil amendment materials—corn straw (A), fly ash (B), sandy soil (C), humic acid (D), and desulfurized gypsum (E)—were adopted. A five-factor, three-level orthogonal experiment was designed to systematically evaluate the improvement effects of different material combinations on the physicochemical properties and nutrient content of the alluvial soils, and to analyze its influence on the growth of Sophora japonica. The results showed that synergistic effect of organic and inorganic multiple materials could effectively improve soil physicochemical properties. Specifically, sandy soil significantly improved the particle size distribution of the alluvial soils, while humic acid and corn straw notably increased soil organic carbon, available nitrogen, and available phosphorus. The synergistic effect of plant growth and amendments facilitated the formation of micro-aggregates and enhanced nutrient activation capacity. Through comprehensive evaluation, An organic enhancement strategy driven by highly active humic acid, combined with moderate amounts of inorganic materials, constitutes the optimal soil amendment formula for Yellow River alluvial soils. Treatment A2B2C1D3E2 (2% corn straw + 1% fly ash + 0.9% humic acid + 1% desulfurized gypsum) performed optimally in improving soil structure, enhancing water retention and nutrient supply capacity, regulating soil pH, and promoting Amorpha fruticosa growth, and can thus be recommended as the preferred formula for ecological restoration of the Yellow River alluvial soils. It establishes a synergistic remediation pathway characterized for Yellow River Alluvial Soils by “sand-based silt modification, waste-based waste treatment, and plant-enhanced efficacy,” providing theoretical foundations and technical approaches for the resource utilization and vegetation restoration of Yellow River Alluvial Soils.