Photoemission spectra are measured for Yb covered surface of wet-chemically-etched H-Si (111). The results reveal that the lattice structure of the H-Si (111) surface is stable against the deposition of Yb atoms. X-ray photoemission spectra indicate the formation of a polarized (dipole) surface layer, with the silicon negatively charged. Ultraviolet photoemission spectra exhibit the semiconducting property of the interface below one monolayer coverage. Work function variation during the formation of the Yb/H-Si (111) interface is measured by the secondary-electron cutoff in the ultraviolet photoemission spectral line. The largest decrease of work function is～1.65eV. The contributions of the dipole surface layer and the band bending to the work function change are determined to be～1.15eV and～0.5eV,respectively. The work function of metal Yb is determined to be～2.8040.05eV.