Arbuscular mycorrhizal (AM) fungi are one of the widely spread micro-organisms, which could form symbionts with more than 80% of the vascular plants in natural ecosystems. It has been showed that AM symbionts could improve plant nutrients and water absorption; increase the resistance ability to stress conditions, thus AM fungi could enhance the host plant growth. The plant soil-borne diseases caused by soil-borne pathogens, including fungi, nematodes and bacteria, are considered as one of the most difficult controlling diseases in agriculture ecosystem. Previous studies have been demonstrated that AM symbionts could increase plant resistance to diseases, and to antagonize soil-borne pathogens. Thus, using AM fungi as a biological control method to antagonize soil-borne pathogens has received increasing interests by phytopathologists and ecologists. On the basis of this, the mechanisms of resistance to diseases induced by AM fungi were summarized in this paper. Mechanisms covered in this review include root morphology alteration, regulation of secondary metabolite production, improvement of rhizosphere environments, competition with pathogenic microorganisms on invasive sites and on nutrition distribution in host plants, and formation of defense systems in plants. Firstly, the characteristics of root morphology alterations were explained, including how AM fungi influence their structures and functions. Secondly, the regulation of AM fungi to secondary metabolites was illustrated. Several types of products, including phytoalexin, callose, alkaloid and phenols were reviewed. Thirdly, AM fungi could improve the rhizosphere environments by influence soil physical and chemical proprieties, and enhance the growth of other beneficial microorganism in rhizosphere soil. Fourth, AM fungi could compete with pathogenic microorganisms. The two kinds of microorganisms maybe compete for the same invasive sites in root systems, and thus they could regulate the nutrition distribution. Fifth, AM fungi could induced the host plant to form the defense systems in plants, including improvement the concentrations of phytohormone, induced the production of signal substrates, regulation of genes expression and enhanced the proteins production, thus AM fungi could enhance the resistance ability of host plant to pathogenic microorganisms. The aim of this paper was to enhance the potential use of AM fungi as a biological control method for preventing plant diseases in future.