Diverse bacteria colonize on the surface of or inside the spores and/or hyphae of arbuscular mycorrhizal fungi (AMF). These bacteria are termed AMF-associated bacteria in literature. AMF-associated bacteria are abundant in species and they distribute widely. The niches of AMF-associated bacteria include the surface and the interior of spore wall, the cytoplasm, the hyphae, the sporocarps etc. The possible biological implications of AMF-associated bacteria involve in some processes such as affecting spore germination, hyphae growth, and the colonization of roots by AMF. Due to the close relationship between AMF and their associated bacteria, they are of great importance in the fields of AMF and soil microbe ecology. Researches on AMF-associated bacteria have been over 30 years world-wide, and the progresses achieved therein are reviewed in this paper.