Abstract: The anodic oxidation surface treatment of carbon fibers in 3-D braided preform was studied. The effects of treatment parameters on the properties of 3-D braided carbon fibers composites were examined in terms of interfacial strength, impact strength and compressive strength, and the fracture of the composites was characterized by SEM. The results indicate the method can treat the surface of carbon fibers not only in the outer layer region but also in the inner region of the braided materials. Moreover, the interfacial strength of the 3-D braided carbon fiber/phenolic resin has been improved obviously and the integrated property of composites has also been improved.