Nitrogen-fixing plants are one of the essential functional groups in terrestrial ecosystems，which drive the accumulation of fixed N on long time scales in many land-based ecosystems. Many researches had showed that the functions of nitrogen-fixing plants are diversity and complex, and they strongly dominate many ecosystem processes. Through forming symbiosis with different diazotrophs, they could ameliorate soil physical and chemical properties and microhabitat. They directly affect the key ecological process, such as nitrogen, phosphorus and carbon cycles, seed germination, seedling establishment, plant growth, succession trajectory and litter component and decomposition. They improve the primary production, community complexity and species diversity in ecosystem, and facilitate ecological restoration and weaken soil, water and nutrient loss. In the future, the following topics, including the quantified research in natural ecosystems, the primary factors limiting to nitrogen fixation and mechanism of ecological control and distribution of nitrogen fixation, should be studied in detail, which could provide insight and theoretical foundation for restoration of degraded ecosystems.