Abstract: Aimed to investigate the influence of arbuscular mycorrhizal fungi (AMF) inoculation on trait of aggregate, a pot experiment was carried with Triticum aestivuml (wheat) as host plants and two different arbuscular mycorrhizal fungus, Glomus intraradices and G. mosseae were inoculated under two phosphorus supplied level. After harvest, soil were screened through sieves with different sizes and then the amounts of different size of aggregates were measured to obtain geometric mean diameter, mean weight diameter and fractal features of soils, path analysis was also used to checkup the indirect or direct factors. The results showed that mycorrhizal inoculation increased soil organ matter concentration, glomalin related soil protein (GRSP) concentration and the amount of water stable aggregate (WSA) significantly compared with the non-mycorrhizal treatments. Mean weight diameter (MWD) and geometric mean diameter (GMD) of mycorrhizal soil were significantly higher than that of non-mycorrhizal soil while mycorrhizal inoculation decreased the value of fractal dimension (D) of mycorrhizal soil compared with the non-mycorrhizal soil. Our results indicated the important role of arbuscular mycorrhizal inoculation in improving quality of soil structure. The Path analysis results showed hyphae density had the highest index on WSA amount through direct effect mainly. The GRSP and organic matter had higher effects on WSA amount as well. For improving soil structure, the role of G. mosseae was better than that of G. intraradices.