The result of the separation and cultivation test of a root-rot disease showed the pathogen was Armillaria ostoyae, compared with the tissue and the carpophore, the rhizomycelium was a more fittable separating material. The pathogen can grow well on the medium of the substrate of synthesized potato juice. The colony became white and turned into black-brown after three days and grew out rhizomycelium after five or six days. The optimal temperature of the three isolations growth is 25℃ and the optimal pH is 6.0~6.4. The best carbon sources were dextrose and maltose. The best nitrogen sources were carbamide and zymoid powder. But they couldn’t grow well on inorganic nitrogen sources of KNO3 and (NH4)2HPO4. The lab experiment results of the pathogen sensitivity to fungicides showed that the CuSO4, mancozeb and chlorothalonil which were used at the concentration of 5mg/mL, 1.25mg/mL and 1.25mg/mL respectively could control and cure the root-rot disease effectively. The result of indoor confrontation test showed the six mycorrhizal fungi, such as Suillus grevillei , and two fixing engineering fungi have restraint action on A5.92, the restraint action of S. greville, Cortinarius russus and Laccaria laccata were the strongest compared with the other fungi. They not only produced the most distinct inhibition zone and restrained the growth of pathogen, but also bestrowed the pathogen and grew on it. So it could be used for biological control of root-rot disease.