Arbuscular mycorrhizal fungi （AMF） are key symbiotic microorganisms that support nutrient acquisition by grassland plants and contribute to soil structure maintenance. This review synthesizes current progress on how different forms of carbon input， nitrogen addition， and their interactions influence AMF in grassland ecosystems， focusing on colonization， hyphal growth， community composition， and symbiotic network structure. Elevated atmospheric CO₂ mainly promotes AMF hyphal growth and biomass accumulation by increasing belowground carbon allocation in plants. Biochar application and organic fertilizer addition improve soil physical properties and nutrient retention， thereby facilitating AMF colonization and community recovery. In contrast， the effects of soluble organic carbon inputs are moderated by plant functional group identity and nitrogen-phosphorus availability. Long‑term or high‑intensity nitrogen addition generally suppresses AMF， a response closely associated with soil acidification， reduced carbon allocation to mycorrhizae， and reorganization of AMF communities. The interactive effects of carbon inputs and nitrogen addition are constrained by carbon source characteristics， nitrogen legacy effects， and the availability of soil nutrients. Future research should increase the comparability of carbon input studies， clarify the combined regulatory roles of carbon source， nitrogen addition intensity and duration on AMF responses， and provide theoretical support for soil nutrient management and degraded grassland restoration.

Arbuscular mycorrhizal fungi  /  Grassland ecosystem  /  Carbon input  /  Nitrogen addition  /  Mycorrhizal symbiosis