Using Green's function approach and the Kubo formula,have studied the electronic transport in metallic films.Taking into account the quantum size effects and the scattering of impurities and two rough surfaces,we calculate the one-particle Green's functions and the in-plane conductivity.It is found that (1) the density of electrons,the impurity mean free path,and the conductivity in a metallic film show oscillations as a function of its thickness with a period of half the Fermi wavelength;(2) under the approximation of the lowest order in the surface scattering,the conductivity formula obtained can reduce to the quasiclassical result suitable for thick films as well as the previous quantum formula for thin films.