Abstract: The three dimensional carbon fiber reinforced SiC composites (C/SiC) were studied by using XPS,small area XPS and imaging XPS.The results show that Si in surface layer of the composites is oxidized to silicon oxides.The impurities of Fe,Na,Ca and Al are present after heating the composites in combustion gas at 1300 ℃. Beneath the surface layer,silicon is present in the forms of elemental Si,SiC and Si oxides in which elemental Si is produced by infiltration of molten silicon.The results of small area XPS multipoint analyses for the cross section of composite show that the relative content of elemental Si decreases with increasing distance from the cross section edge while the relative content of SiC increases with increasing the distance.The Si 2p XPS images show clearly that SiC is deposited in the boundary region between carbon fiber bundles.However,the content of elemental Si is higher in the margin area than in the center area of the cross section.The thickness of SiC between carbon fiber bundles in the center area and the thickness of elemental Si rich layer in the margin area of the cross section have been estimated by using the line scans of the XPS images.