Abstract: To address the dual challenges of heavy metal pollution and soil acidification prevalent in southern China, this study investigates the synergistic immobilization effects and resistance mechanisms of combined applications of calcium-based alkaline materials with phosphorus and iron-based materials on heavy metals in contaminated soils. Cd and Cu contaminated soils were targeted, with calcium carbonate (Ca), disodium hydrogen phosphate (P), and zero-valent iron (Fe) used as amendments. Soil incubation experiments and acid rain leaching experiments were conducted. Results show that the Ca, Fe, and P contained materials significantly reduced the bioavailability of Cd and Cu in the soil, with the Ca-P-Fe combination exhibiting the optimal performance. This combination significantly minimized the active fractions of Cd and Cu by increasing the soil pH and Fe_a content. Range analysis indicated that Fe in Ca-P-Fe combination was most effective in controlling ECA-Cd activity, while Ca was most effective for ECA-Cu. Under long-term acid rain stress (simulating 25~100 years), the Ca-P-Fe combination remiained effective in immobilizing the bioavailability of Cd and Cu, with ECA-Cd and ECA-Cu decreasing by 25.65% and 14.78%, and soil pH increasing by 2.58. These findings validiate that the Ca-P-Fe combination exerts significant synergistic immobilization effects on Cd and Cu contaminated soils and maintains stable immobilization performance under long-term acid rain stress.