1.College of Geoscience and Surveying Engineering， China University of Mining and Technology-Beijing，Beijing ，China；2.State Key Laboratory of Coal Resources and Safe Mining， China University of Mining and Technology-Beijing，Beijing ，China

Coal mining subsidence leads to the degradation of surface soil quality and affect plant growth and rhizosphere environment in mining areas.Arbuscular mycorrhizal fungi， as a kind of beneficial symbiotic fungi， can promote plant growth.In order to evaluate the ecological effect and time-effect of artificial mycorrhizal inoculation in coal mining subsidence area，we take alfalfa planted in Huojitu subsidence area of Shendong Coal Mining Area for 4 years as the research object， and investigated plant height， SPAD， above-ground biomass，infection rate， mycelium density as well as rhizosphere soil characteristics between the inoculation treatment and the control treatment and their interrelationships.We also study the effect of AMF inoculation on alfalfa growth and rhizosphere soil characteristics in coal mining subsidence areas.The results showed that AMF inoculation treatment increased the plant height， SPAD and biomass by 18.2%， 8.3% and 10.4% compared with the control， respectively.Alfalfa could form a good symbiotic relationship with AMF， and the mycorrhizal infection rate and mycelium density was increased by 35% and 34.1% compared with the control group， respectively.Inoculation of mycorrhiza improved rhizosphere soil characters， the inoculation treatment significantly enhanced soil available nitrogen， available phosphorus， organic matter， phosphatase activities by 21.4%， 20.7%， 22.5%， 36.9%， respectively.Correlation analysis showed that mycorrhizal infection rate was significantly positively correlated with plant height， biomass， phosphatase and available phosphorus， while mycelium density was significantly positively correlated with SPAD and organic matter，and showed a highly significant correlation with plant height and biomass.After 4 a reclamation， inoculation of mycorrhiza could significantly promote the growth of alfalfa， increase plant biomass， and effectively improve the quality of rhizosphere soil， which has good ecological effect.