Abstract: Boric acid was used as a protecting agent on C-Cu fiber surface to solve the oxidizing problem while compounding C-Cu/Al composites. The effects of boric acid on the performance of the composites were analyzed through SEM, XRD and tensile tests. The results show that carbon fibers coated with copper are little only a oxidized when pretreated with 1.0% boric acid solution. These carbon fibers in the composites are finely dispersed and have good cohesion with the matrix. Besides, such an amount of boric acid does no harm to the mechanical properties of the composites.