This paper is to study the influence of Ar+ energy of bombardment Cu target and low energy assisted bombardment on Cu-W film structure in the preparation of Cu-W thin film by dual ion beam sputtering technique with iron as the substrate and argon as ion source. The results shown : when Ar+ energy of bombardment tungsten target is about 3keV, the beam of copper target is 20mA, Ar+ energy of bombardment Cu target is 1kev, 1.5kev and 2keV respectively, Cu-W thin film prepared by ion beam sputtering exists with the skeleton of tungsten in amorphous phase mixing with copper grains; with the increase of Ar+ energy of of bombardment copper target, the grain size of copper increases slightly; influenced by crystal defects and lattice distortion, copper diffraction peak offsets a little. Low energy assisted bombardment helps to increase grain growth of copper and can decrease crystal defects and lattice distortion. But with excessive energy, thin film fails to deposit.