Degraded ecosystems pose a severe threat to global biodiversity and ecological security, and understanding the role of plant-microbe interactions (PMI) in ecological restoration has become a research focus. This study systematically investigated the functional mechanisms of PMI in three typical degraded ecosystems (desertified grassland, mining area, and deforested land) across different continents. By combining high-throughput sequencing, metabolomic analysis, and microbial isolation culture, we revealed that PMI promotes ecosystem restoration through multiple pathways: (1) plant root exudates shape rhizosphere microbial communities, enriching beneficial microbes (e.g., nitrogen-fixing bacteria, mycorrhizal fungi); (2) symbiotic microbes enhance plant stress resistance by regulating hormone synthesis and nutrient acquisition; (3) microbial communities accelerate soil organic matter accumulation and nutrient cycling, improving soil fertility. The effectiveness of PMI in restoration varied with ecosystem type, with the strongest promotion effect observed in desertified grassland and the weakest in mining areas. Structural equation modeling confirmed that plant species richness, soil organic carbon content, and moisture were the key factors regulating PMI functional efficiency. Our findings clarify the core functional mechanisms of PMI in degraded ecosystem restoration and provide a theoretical basis for developing microbe-assisted ecological restoration strategies.