Cu-MgF2 nanoparticle cermet films with the copper volume fraction of vol.10%-30% were prepared by rf magnetron co-sputtering deposition and analyzed by x-ray diffraction, x-ray photoelectron spectroscopy and temperature-varying four-wi re technique. Microstructure analysis shows that the cermet films are made of m ainly amorphous MgF2 matrix with embedded fcc-Cu nanoparticles. The a verage si ze of Cu nanoparticles increases from 11.9nm to 17.8nm as Cu content rises fro m vol.10% to vol.30%. The results of electrical conductivity from 50 to 300K sho w that when Cu volume fraction is between 15 and 20%, the film shows a percolati on threshold qCM, and the electric conductivity changes～e ight orders. T he active energies of doping and the intrinsic conductivity of the cermet films and their contributions to the film electrical conductivity are discussed. Based on the percolation theory, the percolation threshold of Cu-MgF2 cerm et film is discussed as well.