Abstract: Ecological restoration of abandoned mines includes root strain injury caused by underground coal mining and geological disaster prevention and control of open-pit slope.Abandoned mines have fragile ecology and low plant survival rate, so ecological restoration has become the main goal of mine environmental governance.Microbial remediation technology is used to restore root function, which has become a research hotspot.In order to reveal the effects of two symbiotic fungi, arbuscular mycorrhiza fungi(AMF)and dark septate endophytes(DSE), on the tensile strength of roots and the shear strength of root-soil composite, the Medicago sativa was taken as the research object.The indoor pot experiment was conducted, and five treatments were set:control CK1 without plant and fungus inoculation, control CK2 with plant and no fungus inoculation, AMF with simple fungus inoculation, DSE with simple fungus inoculation and AMF+DSE with double-fungus inoculation.The effect of fungus inoculation on the root mechanical properties and shear strength of mycorrhizal composite soil was studied.The results showed that the grain size composition of soil inoculated with bacteria in control treatment was almost consistent:fine sand > medium sand> coarse sand.The proportion of coarse sand in soil composition increased and the content of fine sand decreased exponentially before and after inoculation.The average tensile strength of single root and shear strength of composite under five different treatments from high to low were as follows:AMF+DSE> DSE> AMF> CK2.The average tensile strength of single root from high to low was as follows:AMF+DSE> CK2> AMF> DSE.The cohesive force of mycorrhizal composite soil at different depths of 10-20 cm and 20-30 cm was significantly higher than that at depths of 30-40 cm under five treatments, and the cohesive force was related to the distribution of root system.There was an optimal root diameter for the cohesion of root-soil composite with different treatments, namely the cohesion reached the maximum when the root diameter was about 0.6 mm.The research results provide a new mechanical method for microbial reclamation mechanism, and a new idea for biological impairment and restoration of underground coal mining and geological disasters.