Neotyphodium/Epichloë endophytes are widespread symbionts of grasses that asymptomatically inhabit aerial host tissues, and not only confer tolerance to biotic and abiotic stresses, but also affected different kinds of microbes. This paper mainly summarized the effects of grass endophytes to pathogenic fungi, arbuscular mycorrhizal fungi (AMF) and soil microbial community, and the related mechanisms. It was found that many species of pathogen fungi are inhibited by grass endophytes, although some studies demonstrated that grass endophytes had competitive and inhibited effects to AMF, the argument was still controversial. Especially, some researches in recent years demonstrated that the interaction between endophytes and AMF was changed based on different species of both fungi. Furthermore, the structure and function of soil microbial community were also affected by grass endophytes. The effects of endophyte infection on soil microbial community function and structure were relatively subtle and variable across time and soil type. The mechanisms of grass endophytes on pathogenic fungi mailly included: niche space competition, anti-fungal substances production and induced resistance etc.; on AMF maily included: root exudates inhibition, nutrient regulation and infection conditions etc.; on on soil microbial community mainly included: rhizodeposition and litter degradation etc. Alkaloids are important second metabolites by symbionts of endophyte and grass, they could deter herbivores, including insects, and reduce the invasion and colonization from pathogenic fungi; other secondary metabolites in root exudates from host plants can inhibit root colonization of AMF and affect the soil microbial community structure and function. Therfore, the role of grass endophytes in plant-microbe systems should be paid more attention and give priority support for researches.