Abstract: In the present study, to overcome the shortcomings of particulate reinforced composites such as low strength, high brittleness and poor machinability, fine and near sphere particulates were used as reinforcement of LD2 Al alloy matrix composites, with their average size of only about 0.15μm. The tensile properties of as cast and extruded Al₂O₃ P/LD2 composites at room and elevated temperatures were measured. The microstructures of the composites were observed. The results showed that when the sizes of reinforcements were within submicron scale, no dislocation caused by mismatch of CTE was found in the matrix and the strengthening mechanism was changed. In the range of volume fraction of 30%?40%, the tensile strength and elongation of the composites were about 640?760MPa and 8.6?2% respectively, and the strengthening rate was 212%. Superior strength ductility and machinable property of the Al₂O₃ P/LD2 composites were obtained.