【Objective】 In most soils, TP (total phosphorus) is generally plenty, but its availability to plants is very low. When the soil is getting acidified, soil Al is liable to get activated and then bound with HPO₄^2-,H₂PO₄^-, and PO₄^-, turning them into hard-to-dissolve P, thus further lowering soil P availability. Some ectomycorrhizae (EM) are found to be able to deactivate soil Al, thus letting Al-complexes release bonded P in available form, for plants to take up. That is to say, some EMs could be introduced into acid soils to improve soil P availability and plant growth. In experiments of in vitro cultivation of EM fungi, some demonstrated their ability to raise P availability in soils neutral or slightly acidic, but little has been found in the literature validating such ability in the field. The present study aimed to assess effects of inoculation of EM fungi on inorganic P availability and Al activity in the rhizosphere soil of saplings planted in acid soil, and to explore mechanism of EM colonization improving host plants' resistance to Al toxicity. 【Method】 Germinating Pinus massoniana seeds, inoculated with three strains of Laccaria bicolor, namely Lb 270, Lb S238A, and Lb S238N, separately, were imbedded into pots of cold sandy yellow soil collected from a P. massoniana stand, and irrigated twice a day to maintain a proper moisture regime for 16 weeks under the natural conditions. At the end, comparison was made of Pinus massoniana saplings inoculated with EM fungi with those in the control (without inoculation). 【Result】 Results show that inoculation of L. bicolor significantly affected the contents of inorganic P and labile Al in the rhizosphere soil of the saplings and the effects varied with the strain. Compared with the control, inoculation with any of the three L. bicolor strains significantly improved growth and P and Al, uptake of the saplings. In terms of the effect, the three strains exhibited an order of Lb S238N > = Lb 270 > Lb S238A. Inoculation with Lb270 significantly decreased soil pH, the contents of available P, iron-bound P (Fe-P), calcium-bound P (Ca-P), total Al, and exchangeable Al, and the proportion of exchangeable Al in the fraction of labile Al, but increased the proportion of aluminum-bound P (Al-P) in the fraction of inorganic P, and the contents of labile Al or hydroxyl-Al and their proportions in total Al. Inoculation with Lb S238A significantly reduced Al-P, the proportion of Al-P or Fe-P in the fraction of inorganic P, total Al, labile Al, exchangeable Al, organic-complexed Al, and the proportion of exchangeable Al and organic-complexed Al in the fraction of labile Al, but raised soil pH, the content off available P, the proportion of occluded-P (O-P) in the fraction of inorganic P, the proportion of labile Al in total Al, and proportions of hydroxyl-Al or acid-soluble Al in the fraction of labile Al. Inoculation with LbS238N significantly decreased soil pH, the contents of available P, total Al, exchangeable Al, and the proportions of exchangeable Al and organic-complexed Al in the fraction of labile Al, but increased the content of hydroxyl-Al, the proportion of labile Al in total Al and that of hydroxyl-Al in the fraction of labile Al.【Conclusion】All the findings in this experiment demonstrate that inoculation with L. bicolor can improve the resistance of P.massoniana saplings to Al toxicity, which may be attributed to the ability of the fungi to enhance bio-availability of soil P, but their abilities to lower Al activity vary with strain of the fungi.