A series of copper thin films with different thicknesses are fabricated on glass substrates by vacuum electron beam evaporation technology and subsequent thermal oxidation technology. The crystal structure and element compositions of these copper thin films are characterized by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The absorption spectra and surface enhanced Raman spectroscopy (SERS) activity of these copper thin films are analyzed by using UV-Vis-IR spectroscopy and Raman spectrometer, respectively. With the increase of film thickness, the amorphous state of the annealed thin film samples changes to a polycrystalline state with a preferred orientation in the (111) plane, and the red-shift of absorption edge appears. The single-phase nano-Cu2O thin films are obtained when the annealing temperature is 200 ℃ and the annealing time is 60 min. The SERS activity increases with the increase of light absorbance of the nano-Cu2O thin films.