Surfactant-assisted Co film epitaxy growth on Cu (111) using Pb as a surfactant was studied by means of Auger electron spectra and synchrotron radiation photoemission spectra. The results reveal that with increasing the Co thickness most of the Pb atoms always float on the surface. Compared with 0.7ML (monolayer) Pb, the Co film with 1.5 ML Pb surfactant has more layer-by-layer growth on Cu (111). The predeposited Pb layer can suppress the intralayer diffusion on the Cu (111) surface and effectively increase the Co island density at the initial stage of Co growth. On the contrary, a Pb-Co surface alloy was found during the Co film growth; this may hinder the interlayer diffusion of the deposited Co atoms, which is unfavorable to the layer-by-layer growth. The Pb-Co is also considered to be the main reason why some Pb atoms have been buried in the Co films.