[Objective] The objectives of this study were to investigate whether the bacteria colonized on the surface of extraradical hyphae of arbuscular mycorrhizal (AM) fungi do have the dual functions of N₂ fixation and phosphates solubilization. AM fungi release through extraradical hyphae exudates that are rich in carbohydrates and hence provide a habitat for bacteria to colonize in. The interaction between AM fungi and bacteria in the hyphosphere has been found to promote mineralization of organic phosphorus and organic nitrogen, enhance nutrient acquisition of AM fungi, and further improve nutritional status of the host plant. However, it remains unclear whether the bacteria colonized on the surface of extraradical hyphae of AM fungi do have the dual functions of N₂ fixation and phosphate solubilization. [Method] AM fungal hyphae were collected with PVC tubes and nylon mesh in a maize field, and then N₂-fixing bacteria colonized on the surface of extraradical hyphae of AM fungi were isolated with a nitrogen-free selective medium, purified for DNA extraction and identified through 16S rRNA gene sequencing. NifH gene of the bacterial DNA was amplified with specific primers. Nitrogenase activity of the N₂-fixing bacteria was determined via acetylene reduction assay, phosphorus solubilizing ability was by measuring the diameter of the bacteria colony and phosphorus solubilizing halo in NBRIP solid medium, and IAA (Indoleacetic acid) secretion ability was with the Salkowski colorimetric method. [Result] Twenty-three strains of N₂-fixing bacteria, capable of surviving in N-free media, were isolated from the surface of AM fungal hyphae, and sorted into nine different genera (Paenibacillus and Bacillus in Firmicutes; Microbacterium and Arthrobacter in Actinobacteria; Sphingomonas, Brevendimonas, Variovorax, Xenophilus and Hydrocarboniphaga in Proteobacteria), among which, bacteria in Brevendimonas (six strains, accounting for 26% of the total) and Microbacterium (six strains, for 26%)were the highest in relative abundance; eleven strains showed nitrogenase activity, peaking up to (2.97 ±1.32) nmol·mg^-1·h^-1; twelve strains did the ability to solubilize organic phosphorus (phytin); eleven strains did the ability to solubilize sparingly soluble inorganic phosphates (tricalcium phosphate); eight strains did the ability to solubilize both phytin and tricalcium phosphate, with the former being higher than the latter; sixteen strains did the ability to secrete IAA, peaking up to (688.00 ±19.17) μg·mL^-1; and six strains did all the functions, nitrogenase activity, phytin solubilization, sparingly soluble inorganic phosphates solubilization, and IAA secretion, and they belong to five different genera (Brevundimonas, Microbacterium, Sphingomonas, Paenibacillus, and Arthrobacter) and among them, Paenibacillus was the highest in ability of N₂ fixation, sparingly soluble phosphates solubilization, and IAA secretion. [Conclusion] A variety of strains of bacteria with nitrogen-fixing, sparingly soluble phosphates-solubilizing and growth-promoting ability are found colonized on the surface of extraradical hyphae of AM fungi in the maize field. These bacteria with multiple functions may have the ability to greatly expand the pathways for mycorrhizae to absorb nutrients in the soil.