Abstract: Al₂O₃-Mo₃Si/Mo₅Si₃ nanocomposite powders were synthesized by mechanochemical reduction method with MoO₃,Si and Al powders as raw materials.The solid-state reaction process and synthesized composite powders were investigated by XRD,laser particles size analytic instrument,TEM,SEM and DTA-TG method.Experimental results indicated that Al₂O₃-Mo₃Si/Mo₅Si₃ composite powders were obtained by milling of MoO₃-Si-Al powders for 5 h by the mechanical induced self-propagating reactions.The grain sizes of Mo₃Si,Mo₅Si₃ and Al₂O₃ were 27.5 nm,23.3 nm and 31.8 nm respectively after milling of 20 h.The composite powders possessed nano-crystalline structure and the average particle size was 3.988 μm,with spherical shapes and uniform distribution after 20 h.DTA analysis results showed that the first reaction was a thermite reaction of MoO₃ and Al in the milling process,followed by a series of reactions to form Mo₃Si and Mo₅Si₃ in the Mo-Si system.