Cu-Al₂O₃ composite sheets were prepared by the internal oxidation of Cu-0.50 wt.%Al alloy sheets at 900 ℃ for 25 hours. Enrichment extraction method was used to extract Al₂O₃ phase in Cu-Al₂O₃ composites. The type, distribution, relationship with the Cu substrate interface of Al₂O₃ phase in the Cu-Al₂O₃ sheets were studied by TEM. The extracted powder was studied by X-ray diffraction (XRD) and TEM. The results show that theSprecipitated phases of Cu-Al₂O₃ composites by the internal oxidation of Cu-Al alloy sheets are mainly γ-Al₂O₃, and a few of α-Al₂O₃ and θ-Al₂O₃ were precipitated. The Al₂O₃ particles wereSdistributedSin theSCu matrix and completely coherent with the Cu matrix. From the surface to the deep of 0.5 mm,the size of Al₂O₃ particles is reduced from 14 to 5 nm and the spacing of Al₂O₃ particles is reduced from 10 to 15 nm.