Arbuscular mycorrhizal fungi (AMF) can form mutualistic symbioses with most of land plants. AMF can enhance nutrient uptake by plants and increase plant resistance to various adverse abiotic and biotic stresses. AMF and plant parasitized nematodes are all indigenous soil organisms and therefore co-exist in plant roots to finish their life cycle, but the potential role of AMF and nematode are totally reversed. The interaction between AMF and plant-parasitic nematodes have become one of the hot topics in AMF research. This paper focused on the direct and indirect roles of AMF in plant resistances to diseases. The following aspects were discussed: the direct competition between AMF and plant pathogens, the enhancement of plant growth and nutrient uptake, the changes of the root morphology and architecture, the alteration of root exudates and composition and distribution of soil microorganims in the rhizosphere, and the prime of plant defense reactions. It aims to deepen the understanding on the biological functionality of AMF and to explore its potential application in agriculture practices in future.