Carbon fibers could be deposited uniformly with duplex coatings of nickel (the internal layer) and copper (the external layer) using an electroplating process. The thickness of Ni and Cu coatings was about 1-2 mu m. Furthermore alloying between Ni and Cu films and alloying between Cu and base Mg alloy occurred respectively after hot pressing (673 K, 2.5 MPa). In particular the strain to failure of magnesium composites with Ni-Cu-coated carbon fibers was 0.7% higher than that (1.81%) of magnesium composites with untreated carbon fibers.