【Background】Many alien plant species including Ageratina adenophora can establish a mutualistic symbiotic relationship with arbuscular mycorrhizal fungi (AMF) in their newly invaded habitats. Therefore, how these alien species invasions are mediated by mycorrhizal fungi urgently needs to be explored. 【Method】To explore the feedback of soil fungi, including AMF to the invasive plant A.adenophora, the soil chemical properties at different invasion stages (A.adenophora grown with native plants around ［Partially invaded habitats］; and grown as its single species ［Invaded habitats］) were measured, and then the feedback of soil fungi including AMF to A.adenophora were investigated in the field with fungicide treatment. 【Result】The chemical properties of soil were changed under A.adenophora invasion. Fungicide decreased the leaf area, carbon, nitrogen, phosphorus, and δ13C content of A.adenophora. 【Conclusion and significance】Synthetic analysis found that soil fungi increased the carbon and the δ13C content of A.adenophora leaves, but didn′t increase the photosynthesis of A.adenophora in partially invaded habitats, indicating that the increased carbon and δ13C content of A.adenophora leaves was not the result of photosynthesis but of some other mechanism. We supposed that carbon was transported from the soil or adjacent native weeds to A.adenophora through a mycelial network in partially invaded habitats. The changes in soil nutrients at different invasion phases may be one mechanism of A.adenophora invasion, and favors its establishment via fungi especially AMF, and transfer of carbon from soil or native plants stimulates its further spread.