Abstract: Background In recent decades, rapid mineral resource exploitation in China has severely disrupted surface vegetation, altered hydrogeological structures, and degraded local ecosystems. In mountainous plateau regions such as Yunnan Province, large expanses of bare rock slopes—often in high-rainfall zones—have emerged. These disturbed slopes are highly susceptible to landslides, rockfalls, and severe soil erosion, posing long-term threats to both ecological integrity and human safety. There is an urgent need for eco-friendly, cost-effective restoration materials that can enhance slope stability while promoting ecological recovery. Cassava starch, a renewable biopolymer, and peat, an organic-rich substrate with high water and nutrient retention, show potential for such applications. However, their synergistic effects, particularly in improving lateritic red soils in high-altitude environments, remain poorly understood. Methods In this study, lateritic red soil from a Yunnan mining site was amended with cassava starch, grass peat, peat, wheat straw, sawdust, and compound fertilizer. Laboratory tests—including direct shear, permeability, water retention, erosion resistance, and plant growth experiments were conducted to systematically evaluate the mechanical and ecological performance of various amendment mixtures. The entropy weight method was applied to integrate multiple evaluation indicators and determine the optimal amendment ratio. Results Experimental results indicate that Cassava starch significantly increased soil shear strength, with the highest increase of 18.9% observed at a 3% concentration; however, mix in all materials, the most significant effect was achieved at a cassava content of 1%.Cassava starch also notably decreased soil erosion rates, achieving a reduction from 77.53% in untreated soil to 4.82% at the highest concentration tested. Water retention was enhanced, reaching a maximum rate of 28.04% with increased cassava starch. In terms of permeability, the addition of various materials reduced the permeability coefficient by nearly an order of magnitude compared to the pure lateritic soil sample. Plant growth trials demonstrated that while increased peat content slightly suppressed seed germination, it greatly increased plant biomass, reaching a peak biomass of 12.18g. According to the entropy weight analysis, formulation B1 (1% cassava starch and 5% grass peat) achieved the highest comprehensive performance score. Conclusion The proposed amended substrate effectively enhances the mechanical strength, water-holding capacity, erosion resistance, and vegetation growth of mine slopes. Moreover, it provides an optimal formulation for practical engineering applications, demonstrating significant potential and ecological value for mine slope revegetation and soil and water conservation.