ZrAlN/Cu coating has been deposited onto Ti-6Al-4V substrates by reactive magnetron sputtering. The morphology of films was investigated by FESEM, the microstructure was studied by XRD, XPS and TEM. The plastic deformation characteristic of thin films were analysised from loading/unloading curves measured by nano-indentation method. Erosion tests were conducted to evaluate anti-erosion ability. Erosion rates were measured and characteristic damage features were identified on the surface of eroded specimens. The mechanisms of erosion are discussed in order to explain the promising performance of materials in erosive conditions. It was found that there is an significant increase of erosion resistance because of the increase of hardness and toughness.